Patterns of Immunoreactivity with TTF-1 Antibodies 8G7G3/1 and SPT24 Suggest Distinct Immunoprofiles Between Most Pulmonary and Nonpulmonary Small Cell Carcinomas

Introduction. Small cell carcinoma can arise from various sites. Herein, we analyze the ability of 2 thyroid transcription factor-1 (TTF-1) antibodies (SPT24 and 8G7G3/1) to separate pulmonary from nonpulmonary small cell carcinoma. Materials and Methods. We analyzed 26 pulmonary and 83 nonpulmonary small cell carcinomas, and 14 Merkel cell carcinomas. Each tumor was stained with SPT24 and 8G7G3/1. Extent of nuclear staining was scored as diffuse (>50%), focal (11%-50%), rare (1%-10%), or negative (<1%). Results. All pulmonary small cell carcinomas were positive for SPT24 and 8G7G3/1. Four Merkel cell carcinomas (29%) were positive for SPT24 (ranging from rare-to-diffuse), while 2 (14%) showed rare expression with 8G7G3/1. For nonpulmonary small cell carcinomas, 69 (83%) were positive for SPT24 and 40 (48%) were positive for 8G7G3/1. For SPT24 positive tumors, the extent of 8G7G3/1 expression was equal in 17 (25%) and less in 52 tumors (75%), including 29 (42%) that were negative for 8G7G3/1. No nonpulmonary small cell carcinoma had more staining with 8G7G3/1 compared to SPT24. The differences in staining between 8G7G3/1 and SPT24 in the nonpulmonary cohort were statistically significant (P < 0.0001) with no significant difference between primary and metastatic lesions for 8G7G3/1 (P  =  0.66) or SPT24 (P  =  0.77). Conclusion. Most pulmonary small cell carcinomas are diffusely positive for both SPT24 and 8G7G3/1, whereas most nonpulmonary small cell carcinomas exhibit focal-to-no staining with 8G7G3/1 and significantly less staining with 8G7G3/1 compared to SPT24. However, these trends are not absolute and should be interpreted in conjunction with clinical and radiological findings.

Mesothelioma of Uncertain Malignant Potential (MUMP) of the Tunica Vaginalis: Proposal for Reclassification as "Complex Mesothelial Tumor of the Tunica Vaginalis"

A well-differentiated papillary mesothelial tumor (WDPMT) and malignant mesothelioma are 2 well-recognized entities arising from the testis tunica vaginalis. Another mesothelial lesion exclusively seen at this site is mesothelioma of uncertain malignant potential (MUMP)-a lesion reminiscent of WDPMT yet demonstrating variable proportions of more complex architectural patterns that could be confused with invasion. MUMP was first described in 2010 with a total of 11 cases reported to date. Herein, we describe 19 additional patients who underwent hydrocelectomy, excision, and/or orchiectomy. Novel morphologic patterns found in addition to the 2010 series include spindle cells, keloidal-type collagen, and multicystic architecture lined by bland mesothelial cells. Clinical follow-up in 9 patients for more than 1 year (1.5 to 22.5 y, median 4.5 y) revealed no evidence of disease recurrence or metastases. Despite greater architectural complexity, MUMP has (1) bland cytology; (2) merging in with WDPMT areas; (3) low mitotic rate and Ki-67 nuclear labeling index; (4) retention of MTAP and BAP1 expression; and (5) benign clinical follow-up. If these cases were malignant mesotheliomas, one would have expected at least some of the patients to demonstrate disease recurrence/progression without adjuvant therapy within the available follow-up time, particularly with limited resection in most patients. Thus, we propose that "mesothelioma of uncertain malignant potential" be renamed as "complex mesothelial tumor of the tunica vaginalis." Using the term "complex" draws a contrast with the simple cuboidal lining and simple papillary architecture seen in WDPMT. Also, labeling the lesion as "tumor" removes the stigmata of "uncertain malignant potential" and "mesothelioma" that are alarming to patients and clinicians, and potentially could unduly lead to more extensive surgery in an attempt at "complete" resection. At the same time, not definitively labeling the lesion as benign allows recommendations for follow-up.

High-Grade, Nonsarcomatoid Chromophobe Renal Cell Carcinoma: A Series of 22 Cases With Novel Molecular Features on a Subset

Chromophobe renal cell carcinoma (ChRCC) is the third most common subtype of renal cell carcinoma and typically exhibits indolent behavior, though a rare subset can exhibit high-grade morphologic features and is associated with a poor prognosis. Although there are limited data on the molecular characteristics of metastatic and sarcomatoid ChRCC, the molecular features of high-grade, nonsarcomatoid ChRCC remain unexplored. Herein, we characterize 22 cases of ChRCC with high-grade, nonsarcomatoid components. High-grade ChRCC frequently demonstrated advanced stage at diagnosis (64% ≥pT3a or N1), with regions of extrarenal extension, nodal metastases, and vascular invasion consisting solely of high-grade ChRCC morphologically. We performed spatially guided panel-based DNA sequencing on 11 cases comparing high-grade and low-grade regions (n = 22 samples). We identified recurring somatic alterations emblematic of ChRCC, including deletions of chromosomes 1, 2, 6, 10, 13, 17, and 21 in 91% (10/11) of cases and recurring mutations in TP53 (81.8%, n = 9/11) and PTEN (36.4%, n = 4/11). Notably, although PTEN and TP53 alterations were found in both high-grade and low-grade regions, private mutations were identified in 3 cases, indicating convergent evolution. Finally, we identified recurring RB1 mutations in 27% (n = 3) of high-grade regions leading to selective protein loss by immunohistochemistry not observed in adjacent low-grade regions. This finding was confirmed in The Cancer Genome Atlas cohort where 2 of 66 cases contained RB1 mutations and demonstrated unequivocal high-grade, nonsarcomatoid morphology. We also detected multiple chromosomal gains confined to the high-grade regions, consistent with imbalanced chromosome duplication. These findings broaden our understanding of the molecular pathogenesis of ChRCC and suggest that subclonal RB1 mutations can drive the evolution to high-grade, nonsarcomatoid ChRCC.

Risk of Biochemical Recurrence in Patients With Grade Group 1 Prostate Cancer With Extraprostatic Extension Treated With Radical Prostatectomy

PURPOSE

We sought to examine the association of extraprostatic extension (EPE) with biochemical recurrence (BCR) separately in men with Grade Group (GG) 1 and GG2 prostate cancer (PCa) treated with radical prostatectomy.

MATERIALS AND METHODS

We reviewed our institutional database of patients who underwent radical prostatectomy for PCa between 2005 and 2022 and identified patients with GG1 and GG2 disease on final pathology. Fine-Gray competing risk models with an interaction between EPE (yes vs no) and GG (GG1 vs GG2) were used to examine the relationship between disease group and BCR-free survival.

RESULTS

The cohort consisted of 6309 men, of whom 169/2740 (6.2%) with GG1 disease had EPE while 1013/3569 (28.4%) with GG2 disease had EPE. Median follow-up was 4 years. BCR occurred in 400/6309 (6.3%) patients. For men with GG1, there was no statistically significant difference in BCR-free survival for men with vs without EPE (subdistribution HR = 0.88; 95% CI: 0.37-2.09). However, for GG2 patients BCR-free survival was significantly worse for those with vs without EPE (subdistribution HR = 1.97, 95% CI: 1.54-2.52).

CONCLUSIONS

Although there is a subset of GG1 PCas capable of invading through the prostatic capsule, patients with GG1 PCa and EPE at prostatectomy experience similar biochemical recurrence and survival outcomes compared to GG1 patients without EPE. However, among men with GG2, EPE connotes a worse prognosis.

Radical prostatectomy cancer grade and percentage of Gleason pattern 4 estimated by global vs individual tumor grading correlate differently with the risk of biochemical recurrence in Grade Group 2 and 3 cancers

OBJECTIVES

There are 2 grading approaches to radical prostatectomy (RP) in multifocal cancer: Grade Group (GG) and percentage of Gleason pattern 4 (GP4%). We investigated whether RP GG and GP4% generated by global vs individual tumor grading correlate differently with biochemical recurrence.

METHODS

We reviewed 531 RP specimens with GG2 or GG3 cancer. Each tumor was scored separately with assessment of tumor volume and GP4%. Global grade and GP4% were assigned by combining Gleason pattern 3 and 4 volumes for all tumors. Correlation of GG and GP4% generated by 2 methods with biochemical recurrence was assessed by Cox proportional hazard regression and receiver operating characteristic curves, with optimism adjustment using a bootstrap analysis.

RESULTS

Median age was 63 (range, 42-79) years. Median prostate-specific antigen was 6.3 (range, 0.3-62.9) ng/mL. In total, the highest-grade tumor in 371 (36.9%) men was GG2 and in 160 (30.1%) men was GG3. Global grading was downgraded from GG3 to GG2 in 37 of 121 (30.6%) specimens with multifocal disease, and 145 of 404 (35.9%) specimens had GP4% decreased by at least 10%. Ninety-eight men experienced biochemical recurrence within a median of 13 (range, 3-119) months. Men without biochemical recurrence were followed up for a median of 47 (range, 12-205) months. Grade Group, GP4%, and margin status correlated with the risk of biochemical recurrence using highest-grade tumor and global grading, but the degrees of these correlations varied and were statistically significantly different between the 2 grading approaches.

CONCLUSIONS

Grade Group, GP4%, and margin status derived by global vs individual tumor grading predict postoperative biochemical recurrence statistically significantly differently. This difference has important implications if results derived from cohorts graded using different methods are compared.

Clinicopathologic Classification of Renal Cell Carcinoma in Patients ≤40 Years Old From Peru

INTRODUCTION

There are scant data on renal cell carcinoma (RCC) from relatively younger patients in South America using contemporary classification.

METHODS

Fifty-nine consecutively treated patients with RCC (≤40 years old) were assessed from the National Institute of Neoplastic Diseases in Peru from 2008 to 2020 (34 males; 25 females), age range of 13 to 40 years.

RESULTS

Most common presenting symptoms were flank pain (n = 40), hematuria (n = 19), and weight loss (n = 12). Associated conditions included 4 patients with proven or presumed tuberous sclerosis and 1 patient with von Hippel Lindau syndrome, all with clear cell RCC. Tumor histopathology was clear cell RCC in 32 of 59 (54%), chromophobe RCC in 6 of 59 (10%), and 5 of 59 (8%) each of papillary RCC and MiT family translocation-associated RCC. Four of 59 (7%) were FH-deficient RCC and 2 of 59 (3%) remained unclassified. The remaining tumors were isolated examples of clear cell papillary renal cell tumor, eosinophilic solid and cystic RCC (ESC RCC), RCC with fibromyomatous stroma, sarcomatoid RCC, and sarcomatoid clear cell RCC. Of the 4 FH-deficient RCCs, none had the classic morphology. The 5 MiT family translocation RCCs had variable morphology. There were 41 tumors without recurrence or metastases, 3 tumors with local recurrence only, 8 tumors with metastases only, and 7 tumors with both local recurrence and metastases.

CONCLUSIONS

The current study demonstrates the importance of special studies in accurately classifying RCC in younger individuals. The distribution of RCC subtypes in younger individuals is similar between 2 representative large institutions of the United States and Peru.

Metastatic Pleomorphic Lobular Carcinoma of the Breast to the Urinary Bladder: A Report of 10 Cases and Assessment of TRPS1 in the Differential Diagnosis With Plasmacytoid Urothelial Carcinoma

CONTEXT.—

Metastatic pleomorphic lobular carcinoma (MPLC) to the bladder is rare and has considerable histologic and immunohistochemical overlap with plasmacytoid urothelial carcinoma (PUC).

OBJECTIVE.—

To distinguish MPLC from PUC morphologically and immunohistochemically, including a newer marker, TRPS1.

DESIGN.—

Ten MPLCs to the bladder were reassessed and stained with estrogen, progesterone, and androgen receptors; GATA3; keratin 5/6; HMWK; GCDFP-15; and TRPS1. Sixteen PUCs constituted controls.

RESULTS.—

We studied 4 transurethral resections of bladder tumors and 6 biopsies from 10 women (median age, 69 years) who had breast cancer on average 15 years prior. Microscopic patterns included single cells and cords of cells (n = 4), nests/sheets of dyscohesive cells (n = 2), or both (n = 4). All tumors had cells with voluminous eosinophilic cytoplasm and eccentric nuclei mimicking PUC, and 7 of 10 tumors had signet ring cells. MPLCs were positive for estrogen (8 of 10), progesterone (3 of 7), and androgen receptors (4 of 10); GCDFP-15 (7 of 10); GATA3 (9 of 10); HMWK (7 of 8); and TRPS1 (7 of 10). No MPLCs stained for keratin 5/6 (n = 9). Of 16 PUCs, 2 showed faint and 2 demonstrated strong TRSP1 staining; 7 of 16 were negative for p63.

CONCLUSIONS.—

MPLC to bladder often presents in patients with a remote history of breast cancer, exhibiting significant histologic and immunohistochemical overlap with PUC. Based on prior works and the current study, estrogen receptor (particularly SP-1), mammaglobin, and p63 help differentiate MPLC from PUC. Keratin 5/6 may aid in distinguishing a less frequent basal type PUC because it is typically negative in MPLC. Some PUCs express TRPS1. Caution should be exercised because immunophenotypes of these tumors greatly overlap, and ramifications of misclassification are major.

Characterization of HOXB13 expression patterns in localized and metastatic castration-resistant prostate cancer

HOXB13 is a key lineage homeobox transcription factor that plays a critical role in the differentiation of the prostate gland. Several studies have suggested that HOXB13 alterations may be involved in prostate cancer development and progression. Despite its potential biological relevance, little is known about the expression of HOXB13 across the disease spectrum of prostate cancer. To this end, we validated a HOXB13 antibody using genetic controls and investigated HOXB13 protein expression in murine and human developing prostates, localized prostate cancers, and metastatic castration-resistant prostate cancers. We observed that HOXB13 expression increases during later stages of murine prostate development. All localized prostate cancers showed HOXB13 protein expression. Interestingly, lower HOXB13 expression levels were observed in higher-grade tumors, although no significant association between HOXB13 expression and recurrence or disease-specific survival was found. In advanced metastatic prostate cancers, HOXB13 expression was retained in the majority of tumors. While we observed lower levels of HOXB13 protein and mRNA levels in tumors with evidence of lineage plasticity, 84% of androgen receptor-negative castration-resistant prostate cancers and neuroendocrine prostate cancers (NEPCs) retained detectable levels of HOXB13. Notably, the reduced expression observed in NEPCs was associated with a gain of HOXB13 gene body CpG methylation. In comparison to the commonly used prostate lineage marker NKX3.1, HOXB13 showed greater sensitivity in detecting advanced metastatic prostate cancers. Additionally, in a cohort of 837 patients, 383 with prostatic and 454 with non-prostatic tumors, we found that HOXB13 immunohistochemistry had a 97% sensitivity and 99% specificity for prostatic origin. Taken together, our studies provide valuable insight into the expression pattern of HOXB13 during prostate development and cancer progression. Furthermore, our findings support the utility of HOXB13 as a diagnostic biomarker for prostate cancer, particularly to confirm the prostatic origin of advanced metastatic castration-resistant tumors. © 2023 The Pathological Society of Great Britain and Ireland.

Adenocarcinomas of the Gynecologic Tract Involving the Urinary Bladder: A Series of 16 Cases Potentially Mimicking Urothelial Malignancy

CONTEXT.—

There is limited literature describing gynecologic adenocarcinomas involving the urinary bladder, and potential diagnostic pitfalls.

OBJECTIVE.—

To describe key features distinguishing metastatic (or extension of) gynecologic adenocarcinomas from urothelial carcinomas with glandular differentiation.

DESIGN.—

Retrospective review of surgical pathology cases of gynecologic adenocarcinomas involving the bladder, from 2 different institutions, retrieved from surgical pathology archives, was performed. Morphologic features were recorded, along with immunohistochemistry results when available. Electronic medical records were reviewed for clinical and radiographic information.

RESULTS.—

Sixteen cases of gynecologic adenocarcinomas (9 endometrial endometrioid adenocarcinomas, 4 endometrial serous carcinomas, 2 high-grade tubo-ovarian serous carcinomas, and 1 cervical adenosquamous carcinoma) involving the bladder were identified. All included cases had mucosal involvement potentially mimicking primary bladder neoplasms, including 4 cases originally diagnosed as urinary carcinomas. Tumors expressed keratin 7 (12 of 13; 92%), PAX8 (11 of 12; 92%), estrogen receptor (11 of 15; 73%), p16 (8 of 11; 73%), progesterone receptor (8 of 14; 57%), GATA3 (5 of 12; 42%), and p63 (3 of 11; 27%); all tumors were negative for keratin 20 (0 of 12). Features supportive of Müllerian origin included prior history of gynecologic malignancy, lack of morphologic heterogeneity in nonendometrioid tumors, and immunophenotypic coexpression of PAX8 and estrogen receptor with absent GATA3. Potential pitfalls seen in a subset of cases included misleading radiologic and cystoscopic findings, replacement of the overlying urothelial mucosa by tumor mimicking precursor lesions, focal GATA3 and/or p63 positivity, and areas of squamous differentiation in tumors of endometrioid histology.

CONCLUSIONS.—

A combination of clinical history, certain morphologic features, and proper selection of immunohistochemical stains is key for the correct diagnosis of secondary gynecologic adenocarcinomas involving the urinary bladder.

Baseline prostate health index risk category and risk category changes during active surveillance predict grade reclassification

BACKGROUND

It is not known whether baseline prostate health index (PHI) at the initiation of active surveillance (AS) or repeated PHI testing during AS is of clinical value after confirmatory biopsy in AS men followed with multiparametric magnetic resonance imaging (mpMRI).

METHODS

We identified 382 AS patients with no greater than Grade Group 1 (GG1) prostate cancer on diagnostic and confirmatory biopsy, at least one mpMRI and PHI test, of which 241 had at least 2 PHI tests. Grade reclassification (GR) was defined as ≥GG2 on surveillance biopsy. PHI risk categories 1 to 4 were as defined by the manufacturer. Associations between baseline PHI risk category or baseline PSA density (PSAD), change in PHI risk categories over time or PSAD changes over time and GR were evaluated with multivariable Cox proportional hazard regression models adjusted for age, Prostate Imaging-Reporting and Data System score and number of positive cores.

RESULTS

Men with baseline PHI scores in the highest risk categories had lower rates of GR-free survival (log-rank P < 0.001), as did those who increased in PHI risk category or remained in a high PHI risk category during surveillance (log-rank P = 0.032). On multivariable regression, baseline PHI risk category was a predictor of GR (risk category 4 [vs. 1] hazard ratio [HR] 2.74, 95% confidence interval [CI] 1.32-5.66, P = 0.002, model C-index 0.764, Akaike Information Criterion [AIC] 797), as were PHI risk category changes over time (risk category 4 [vs. 1] HR 4.20, 95% CI 1.76-10.05, P = 0.002, C-index 0.759, AIC 489). Separate models with baseline PSAD and PSAD changes over time yielded C-indices of 0.709 (AIC 809) and 0.733 (AIC 495) respectively.

CONCLUSIONS

Baseline PHI risk category and PHI changes over time were both independent predictors of GR after confirmatory biopsy, but the added benefit over PSAD seemed modest. However, baseline PHI and PHI risk category changes provided clinically useful risk stratification for time to GR, so further evaluation of PHI's ability to help reduce the frequency of mpMRI and/or surveillance biopsies with more PHI data points over time may be warranted.

Prostate Cancer Radiological Estimation of Change in Sequential Evaluation (PRECISE) Magnetic Resonance Imaging Scoring to Predict Clinical Outcomes in Active Surveillance for Grade Group 1 Prostate Cancer

OBJECTIVE

To determine whether radiological change on serial multiparametric magnetic resonance imaging scored using the Prostate Cancer Radiological Estimation of Change in Sequential Evaluation (PRECISE) Scoring system predicts grade reclassification (GR) at surveillance biopsy in men on active surveillance (AS) with Grade Group 1 (GG1) prostate cancer (PCa).

METHODS

We retrospectively reviewed records of 255 men with low-risk PCa on AS with magnetic resonance imaging (MRI)-informed diagnostic and confirmatory biopsies and studied the subset who had surveillance biopsies (n = 163) within 6months of an interval MRI.

RESULTS

We studied 309 PRECISE scores in 255 men. 14% demonstrated radiological progression (PRECISE 4-5) on interval MRI performed within 24months, compared to 34% of those whose interval MRI was performed at a >3-year interval (P = .002). 28% (46/163) of men undergoing surveillance biopsy experienced GR to ≥ GG2 PCa. There was no significant increase in the rate of GR with increasing PRECISE score (PRECISE 1-2: 24%, PRECISE 3: 23%, PRECISE 4-5: 38%; P = .11). There was a significant increase in the rate of GR with increasing PI-RADS score (P < .05). On multivariable analysis, a PI-RADS score of 4-5 was significantly associated with GR compared to men who had a highest PI-RADS ≤3 (OR=1.98 [95% CI: 1.45-3.09, P = .01]).

CONCLUSION

In a low-risk AS cohort with limited follow-up, a patient's highest PI-RADS rather than their PRECISE score on interval MRI was predictive of GR on surveillance biopsy.

Lipoblastoma-Like Tumor and Fibrosarcoma-Like Lipomatous Neoplasm Represent the Same Entity: A Clinicopathologic and Molecular Genetic Study of 23 Cases Occurring in Both Men and Women at Diverse Locations

Lipoblastoma-like tumor (LLT) is a benign soft tissue tumor demonstrating mixed morphologic features of lipoblastoma, myxoid liposarcoma, and spindle cell lipoma but lacking genetic alterations associated with those tumors. LLT was originally thought to be specific to the vulva but has since been reported in the paratesticular region. The morphologic features of LLT overlap with those of "fibrosarcoma-like lipomatous neoplasm" (FLLN), a rare, indolent adipocytic neoplasm considered by some to form part of the spectrum of atypical spindle cell and pleomorphic lipomatous tumor. We compared the morphologic, immunohistochemical, and genetic features of 23 tumors previously classified as LLT (n = 17) and FLLN (n = 6). The 23 tumors occurred in 13 women and 10 men (mean age, 42 years; range, 17 to 80 years). Eighteen (78%) cases arose in the inguinogenital region, whereas 5 tumors (22%) involved noninguinogenital soft tissue, including the flank (n = 1), shoulder (n = 1), foot (n = 1), forearm (n = 1), and chest wall (n = 1). Microscopically, the tumors were lobulated and septated, with variably collagenized fibromyxoid stroma, prominent thin-walled vessels, scattered univacuolated or bivacuolated lipoblasts, and a minor component of mature adipose tissue. Using immunohistochemistry, 5 tumors (42%) showed complete RB1 loss, with partial loss in 7 cases (58%). RNA sequencing, chromosomal microarray, and DNA next-generation sequencing study results were negative for significant alterations. There were no clinical, morphologic, immunohistochemical, or molecular genetic differences between cases previously classified as LLT or FLLN. Clinical follow-up (11 patients [48%]; range, 2-276 months; mean, 48.2 months) showed all patients were alive without disease, and only one patient had experienced a single local recurrence. We conclude that LLT and FLLN represent the same entity, for which "LLT" seems most appropriate. LLT may occur in either sex and any superficial soft tissue location. Careful morphologic study and appropriate ancillary testing should allow for the distinction of LLT from its potential mimics.

High-Grade Desmoplastic Foamy Gland Prostatic Adenocarcinoma

CONTEXT.—

It is important to recognize high-grade foamy gland prostatic adenocarcinoma with desmoplastic stroma given its aggressive clinical course with frequent metastases and death.

OBJECTIVE.—

To review the morphology, immunohistochemistry, and prognosis for this rare subtype of prostate adenocarcinoma.

DESIGN.—

Twenty-four cases received for consultation from 2010 to 2021 were analyzed including needle biopsy (n = 21), transurethral resection (n = 2), and a cystoprostatectomy (n = 1).

RESULTS.—

Patients ranged in age from 40 to 89 years (mean, 67 years). On average, 8 cores per case were involved (mean 67% core involvement). Extraprostatic extension and seminal vesicle invasion were observed in 6 of 21 (29%) and 3 of 21 (14%) needle biopsy cases, respectively. Twenty of the 24 cases (83%) were Grade Group (GG) 5 with 4 of 24 (17%) being GG4. Tumor necrosis as a component of Gleason pattern 5 was observed in 21 of 24 cases (88%). Associated intraductal adenocarcinoma (IDC) was observed in 22 of 24 cases (92%), with 4 of 24 cases (17%) demonstrating extensive IDC. Diagnostic challenges were as follows: (1) sparse isolated cancer glands embedded in the dense desmoplastic stroma; (2) fragmented glands; and (3) aberrant staining for high-molecular-weight cytokeratin in a nonbasal cell pattern in all cases. PTEN loss was observed in 9 cases, and p53 nuclear accumulation was observed in 8 cases. Three patients were lost to follow-up. Overall, of the 16 patients with meaningful follow-up, 12 (75%) either had metastases or died from prostate cancer.

CONCLUSIONS.—

High-grade desmoplastic foamy gland adenocarcinoma is difficult to diagnose and grade and has a poor prognosis.

Identifying Men Who Can Remain on Active Surveillance Despite Biopsy Reclassification to Grade Group 2 Prostate Cancer

PURPOSE

Men on active surveillance with Grade Group 1 prostate cancer who reclassify to Grade Group 2 on surveillance biopsy often leave active surveillance. We aimed to identify subgroups of men who can safely remain on active surveillance despite preoperative reclassification to Grade Group 2.

MATERIALS AND METHODS

We studied 249 active surveillance patients with surveillance biopsies classified as Grade Group 1 or Grade Group 2 who underwent radical prostatectomy. Perineural invasion, cancer volume, linear length and maximum percentage of Gleason pattern 4, and prostate-specific antigen density were evaluated. Radical prostatectomy adverse pathology was defined by any of: pN1; ≥pT3; ≥Grade Group 2 with ≥20% Gleason pattern 4; intraductal carcinoma; large cribriform glands.

RESULTS

A multivariable logistic regression model incorporating prostate-specific antigen density and perineural invasion stratified radical prostatectomy adverse pathology risk among Grade Group 1 and Grade Group 2 active surveillance patients. 57% (39/68) of Grade Group 1 men reclassified to Grade Group 2 while on active surveillance had favorable radical prostatectomy pathology. Those without biopsy perineural invasion and with low prostate-specific antigen density were more likely to have favorable radical prostatectomy pathology.

CONCLUSIONS

Most Grade Group 1 men who enter active surveillance and subsequently reclassify to Grade Group 2 have favorable findings at radical prostatectomy and can remain on active surveillance. Among patients reclassified to Grade Group 2, those with low prostate-specific antigen density and without perineural invasion had the lowest risk of radical prostatectomy adverse pathology, comparable to (or below) that of Grade Group 1 patients who were not reclassified to Grade Group 2 preoperatively. Prostate-specific antigen density and perineural invasion stratify risk in active surveillance patients reclassified to Grade Group 2 and, if concordant with other clinicopathological and radiographic findings, can enable more patients to remain on active surveillance. Reclassification to Grade Group 2 alone should not disqualify men from remaining on active surveillance.

Nested Subtype of Urothelial Carcinoma in the Upper Urinary Tract: A Series of 15 Cases

Nested subtype of urothelial carcinoma (NVUC) of the upper urinary tract is rare. While this subtype has an aggressive behavior in the urinary bladder, little is known about this subtype in the renal pelvis and ureter. In addition, due to NVUC's bland morphology and resemblance to von Brunn nests proliferation, which can be florid in the renal pelvis and ureter, establishing a diagnosis of NVUC in these sites can be difficult, especially on small biopsies. Nineteen cases of NVUC of the renal pelvis and the ureter were identified. One was in-house and 18 cases were sent to the genitourinary pathology consult service. Four cases were excluded due to difficulty in obtaining the slides from other institutions. In all, 8/15 (53.33%) cases showed large nested morphology, 4/15 (26.66%) cases showed mixed large and small nested morphology, and only 3/15 (20%) cases showed predominantly small nested morphology. In all cases, the invasive component was pure nested subtype, and tumors were all unifocal. In 8/15 cases, there was the presence of an overlying low-grade papillary urothelial carcinoma. An associated desmoplastic stromal reaction was none/minimal in 12/15 (80%) cases, with a prominent reaction in the remaining 3/15 (20%) cases. Pathologic stages for the resections were pT1 (n=1), pT2 (n=3), pT3 (n=8), and pT4 (n=1). There was only 1 case with a lymph node metastasis at the time of resection who had pT4 disease. Follow-up was available in 10/15 cases, 7/10 cases showed no recurrences or metastases, and the remaining 3/10 cases later developed urothelial carcinoma of the bladder. In 5/15 cases, follow-up could not be obtained. Similar to NVUC in the urinary bladder, NVUC in the upper tract typically lacks an associated desmoplastic reaction and has by definition bland cytology. In contrast to NVUC of the urinary bladder, NVUC in the upper urothelial tract is: (1) more frequently associated with an overlying papillary urothelial carcinoma; (2) more commonly has a large nested pattern; and (3) appears to behave less aggressively.

NCCN Guidelines® Insights: Prostate Cancer Early Detection, Version 1.2023

The NCCN Guidelines for Prostate Cancer Early Detection provide recommendations for individuals with a prostate who opt to participate in an early detection program after receiving the appropriate counseling on the pros and cons. These NCCN Guidelines Insights provide a summary of recent updates to the NCCN Guidelines with regard to the testing protocol, use of multiparametric MRI, and management of negative biopsy results to optimize the detection of clinically significant prostate cancer and minimize the detection of indolent disease.

Myoid gonadal stromal tumours are characterised by recurrent chromosome-level copy number gains: molecular assessment of a multi-institutional series

Myoid gonadal stromal tumours (MGST) represent a rare type of testicular sex cord-stromal tumour that has recently been recognised as a distinct entity by the World Health Organization (WHO) classification of genitourinary tumours. MGSTs affect adult men and have been reported to behave in an indolent fashion. Histologically, MGSTs are pure spindle cell neoplasms that coexpress SMA and S100 protein. Given that the molecular features of these neoplasms remain largely undescribed, we evaluated a multi-institutional series of MGSTs using DNA and RNA sequencing. This study included 12 tumours from 12 patients aged 28 to 57 years. Tumour sizes ranged from 0.6 to 4.3 cm. Aggressive histologic features, such as vascular invasion, necrosis, invasive growth, and atypical mitoses were invariably absent. Mitotic activity was low, with a median of less than 1 mitosis per 10 high power fields (HPF; maximum: 3 mitoses per 10 HPF). Molecular analyses did not identify recurrent mutations or gene fusions. All cases with interpretable copy number variant data (9/10 cases sequenced successfully) demonstrated a consistent pattern of chromosome arm-level and whole-chromosome-level copy number gains indicative of ploidy shifts, with recurrent gains involving chromosomes 3, 6, 7, 8, 9, 11, 12, 14q, 15q, 17, 18q, 20, and 21q. Similar findings have also been recognised in pure spindle cell and spindle-cell predominant sex cord-stromal tumours without S100 protein expression. MGSTs are characterised by ploidy shifts and may be part of a larger spectrum of spindle cell-predominant sex cord-stromal tumours, including cases without S100 protein expression.

MED15::TFE3 Renal Cell Carcinomas: Report of Two New Cases and Review of the Literature Confirming Nearly Universal Multilocular Cystic Morphology

We report two novel cases of Xp11 translocation renal cell carcinomas with the MED15::TFE3 gene fusion in adult females aged 40 and 74 years. Both cases were extensively cystic and contained only minimal clear cells lining cysts and within septal walls, raising the differential diagnosis of multilocular cystic renal neoplasm of low malignant potential. By immunohistochemistry, both neoplasms labeled for PAX8, TFE3, cathepsin K and Melan A but not for HMB45. On review of the published literature and the two cases reported herein, over 90% of MED15::TFE3 renal cell carcinomas (RCCs) have been described as cystic. The correlation of the MED15::TFE3 fusion with extensively cystic morphology represents the strongest association of TFE3 fusion partner with clinicopathological features among TFE3-rearranged RCC reported to date.

Genomic Characterization of Prostatic Basal Cell Carcinoma

Basal cell carcinoma (BCC) of the prostate is a rare tumor. Compared with the more common acinar adenocarcinoma (AAC) of the prostate, BCCs show features of basal cell differentiation and are thought to be biologically distinct from AAC. The spectrum of molecular alterations of BCC has not been comprehensively described, and genomic studies are lacking. Herein, whole genome sequencing was performed on archival formalin-fixed, paraffin-embedded specimens of two cases with BCC. Prostatic BCCs were characterized by an overall low copy number and mutational burden. Recurrent copy number loss of chromosome 16 was observed. In addition, putative driver gene alterations in KIT, DENND3, PTPRU, MGA, and CYLD were identified. Mechanistically, depletion of the CYLD protein resulted in increased proliferation of prostatic basal cells in vitro. Collectively, these studies show that prostatic BCC displays distinct genomic alterations from AAC and highlight a potential role for loss of chromosome 16 in the pathogenesis of this rare tumor type.

Mesonephric Adenocarcinoma and Mesonephric-like Adenocarcinoma of the Urinary Tract

Given the association of mesonephric adenocarcinoma (MA) of the uterine cervix with florid mesonephric hyperplasia, one would expect MAs to rarely arise in other anatomical locations that harbor mesonephric remnants. In contrast, mesonephric-like adenocarcinoma (MLA) is thought to arise from Müllerian origin without an association with mesonephric remnants. The current case series characterizes 4 cases of MA arising in the urinary bladder (1 woman and 3 men), 1 case of MA in the perirenal region (woman), and 1 case of MLA in the ureter (woman). All cases displayed morphologic features similar to MA of the uterine cervix and MLA of the ovary and endometrium, characterized by predominant tubular and focal glandular/ductal architecture. Mesonephric remnants in the bladder wall were closely associated with adjacent MA in cases 1 and 4. MLA in case 6 was associated with mesonephric-like proliferations and endometriosis. All cases (6/6) were diffusely positive for Pax8, and all displayed a luminal pattern of CD10 staining, except case 4 for which CD10 immunostain was not available for review. Gata3 was either focally positive (cases 1, 2, and 6), negative (case 3), or diffusely positive (case 5). TTF-1 was diffusely expressed in cases 1 and 3 and negative in cases 2, 5, and 6. Although a KRAS G12C somatic mutation was detected in case 6, hotspot mutations in KRAS, NRAS, and PIK3CA were not present in other tested cases. Our study demonstrates that MAs and MLAs of the urinary tract share similar histopathogenesis, morphology, and immunophenotype to their counterparts in the female genital tract. We propose that, in the urinary tract, MA might be classified as a distinctive tumor that arises from mesonephric remnants or presumed Wolffian origin if they are not related to Müllerian-type precursors. The tumor displaying similar morphology and immunoprofile to MA but associated with Müllerian-type precursors should be classified as MLA.

Genomic Classifiers in Personalized Prostate Cancer Radiation Therapy Approaches: A Systematic Review and Future Perspectives Based on International Consensus

Current risk-stratification systems for prostate cancer (PCa) do not sufficiently reflect the disease heterogeneity. Genomic classifiers (GC) enable improved risk stratification after surgery, but less data exist for patients treated with definitive radiation therapy (RT) or RT in oligo-/metastatic disease stages. To guide future perspectives of GCs for RT, we conducted (1) a systematic review on the evidence of GCs for patients treated with RT and (2) a survey of experts using the Delphi method, addressing the role of GCs in personalized treatments to identify relevant fields of future clinical and translational research. We performed a systematic review and screened ongoing clinical trials on ClinicalTrials.gov. Based on these results, a multidisciplinary international team of experts received an adapted Delphi method survey. Thirty-one and 30 experts answered round 1 and round 2, respectively. Questions with ≥75% agreement were considered relevant and included in the qualitative synthesis. Evidence for GCs as predictive biomarkers is mainly available to the postoperative RT setting. Validation of GCs as prognostic markers in the definitive RT setting is emerging. Experts used GCs in patients with PCa with extensive metastases (30%), in postoperative settings (27%), and in newly diagnosed PCa (23%). Forty-seven percent of experts do not currently use GCs in clinical practice. Expert consensus demonstrates that GCs are promising tools to improve risk-stratification in primary and oligo-/metastatic patients in addition to existing classifications. Experts were convinced that GCs might guide treatment decisions in terms of RT-field definition and intensification/deintensification in various disease stages. This work confirms the value of GCs and the promising evidence of GC utility in the setting of RT. Additional studies of GCs as prognostic biomarkers are anticipated and form the basis for future studies addressing predictive capabilities of GCs to optimize RT and systemic therapy. The expert consensus points out future directions for GC research in the management of PCa.

Prostate Cancer in Male-to-Female Transgender Individuals: Histopathologic Findings and Association With Gender-affirming Hormonal Therapy

Male-to-female (MtF) transgender individuals are at risk for prostate cancer, although guidelines for screening and management in this population are not well established. We describe a series of 9 MtF transgender patients who underwent prostate tissue sampling and highlight histopathologic features and challenges related to pathologic interpretation of prostate tissue in this patient population. Seven of 9 total patients were diagnosed with prostate cancer and all had elevated prostate-specific antigen at the time of diagnosis. Three of the 7 patients diagnosed with prostate cancer had received different types of hormone therapy for gender affirmation before the diagnosis of prostate cancer, and in all 3 of these patients, there was histologic evidence of hormone therapy effect in both benign prostate tissue and/or the adenocarcinoma. The 2 patients with benign prostate tissue underwent transurethral resection for lower urinary tract symptoms and were previously on hormone therapy for gender affirmation. Both of these specimens showed diffuse glandular atrophy and basal cell hyperplasia, indicative of hormone therapy effect on benign prostatic tissue. In the patients diagnosed with prostate cancer, a spectrum of grades was observed, ranging from Grade Group 1 to Grade Group 5. Four patients underwent radical prostatectomy, with 2 cases showing extraprostatic extension and Grade Group 5 prostatic adenocarcinoma, and 2 showing Grade Group 2 prostatic adenocarcinoma. Three of the 4 patients who underwent radical prostatectomy had received gender-affirming hormone therapy before surgery, and all 3 of these specimens showed hormone therapy effect in non-neoplastic prostate tissue and focal hormone therapy effect in prostatic adenocarcinoma. The presence of areas of viable carcinoma without hormone therapy effect enabled the assignment of a Gleason score and Grade Group in these 3 cases. Hormone therapy administered for gender identity affirmation induces histopathologic changes to both benign prostate tissue (nonkeratinizing squamous metaplasia, diffuse atrophy, basal cell hyperplasia, and stromal dominance with decreased numbers of glands) and prostatic adenocarcinoma (nuclear pyknosis, atrophy, cytoplasmic vacuolization, and architectural patterns that would qualify for Gleason 4 and 5 in the absence of hormone therapy effect) that have been traditionally seen in cis-male prostate cancer patients receiving hormone therapy. In the absence of hormone therapy, the morphology of prostatic adenocarcinoma in transgender patients shows classic morphologic features similar to those seen in cis-male patients not on hormone therapy. Prostate cancer with hormone therapy effect may not only be histologically quite subtle and may be overlooked if not suspected, but also should not be assigned a Gleason score because the Gleason score would substantially overstate its biologic potential. Therefore, similar to cis-male patients who have received androgen deprivation therapy for prostate cancer, transgender patients on hormone therapy for gender affirmation may be at risk for both underrecognition and over-grading of prostate cancer, particularly if the pathologist is not aware of the clinical history.

Condyloma acuminatum of the urinary tract demonstrates atypical squamous cells in urine cytology

Urine cytology of urinary tract condylomas has not been systematically studied. We analyzed cytologic features of urinary tract condylomas and evaluated potential diagnostic challenges and pitfalls. We retrospectively reviewed urine cytology of urinary tract condylomas from 2 academic institutions (2015-2022). Among 20 patients with urinary tract condylomas, 6 had urine cytology (2 samples in 1 patient), including 3 men and 3 women (mean age, 74.3 years; range, 65-86 years). Original interpretations were negative for high-grade urothelial carcinoma (NHGUC; n = 4), atypical urothelial cells (n = 1), reactive urothelial cells (n = 1), and negative for malignancy (n = 1). Squamous cells were noted in 3 cases, atypical squamous cells (ASC) consistent with low-grade squamous intraepithelial lesion (LSIL) were noted in 1 case, and in 3 cases, the presence of squamous cells was not mentioned. All urines were reclassified according to The Paris System as NHGUC. Specimens were composed of benign urothelial cells and groups or isolated ASC consistent with LSIL (n = 4), atypical keratinized squamous cells (n = 2), and ASC that did not meet LSIL criteria (n = 1). The LSIL cells showed nuclear enlargement (n = 4), hyperchromasia (n = 4), perinuclear halo (n = 3), nuclear membrane irregularity (n = 4), orangeophilic cytoplasm (n = 3), and binucleation (n = 4). The atypical keratinized squamous cells showed hyperchromasia (n = 2), nuclear membrane irregularity (n = 2), keratin pearls (n = 2), and binucleation (n = 1). The ASC that did not meet LSIL criteria showed nuclear enlargement and orangeophilic cytoplasm. Many urinary tract condylomas (57%) demonstrate classic LSIL features in urine cytology. Less frequent cases can mimic keratinizing squamous cell carcinoma (28%) or demonstrate ASC not diagnostic of LSIL (15%).

Clonal relationships of adjacent Gleason pattern 3 and Gleason pattern 5 lesions in Gleason Scores 3+5=8 and 5+3=8

Genomic studies have demonstrated a high level of intra-tumoral heterogeneity in prostate cancer. There is strong evidence suggesting that individual tumor foci can arise as genetically distinct, clonally independent lesions. However, recent studies have also demonstrated that adjacent Gleason pattern (GP) 3 and GP4 lesions can originate from the same clone but follow divergent genetic and morphologic evolution. The clonal relationship of adjacent GP3 and GP5 lesions has thus far not been investigated. Here we analyzed a cohort of 14 cases-11 biopsy and 3 radical prostatectomy specimens-with a Gleason score of 3 + 5 = 8 or 5 + 3 = 8 present in the same biopsy or in a single dominant tumor nodule at radical prostatectomy. Clonal and subclonal relationships between GP3 and GP5 lesions were assessed using genetically validated immunohistochemical assays for ERG, PTEN, and P53. 9/14 (64%) cases showed ERG reactivity in both GP3 and GP5 lesions. Only 1/14 (7%) cases showed a discordant pattern with ERG staining present only in GP3. PTEN expression was lost in 2/14 (14%) cases with perfect concordance between GP5 and GP3. P53 nuclear reactivity was present in 1/14 (7%) case in both GP5 and GP3. This study provides first evidence that the majority of adjacent GP3 and GP5 lesions share driver alterations and are clonally related. In addition, we observed a lower-than-expected rate of PTEN loss in GP5 in the context of Gleason score 3 + 5 = 8 or 5 + 3 = 8 tumors.

Pathological characterization and clinical outcome of penile intraepithelial neoplasia variants: a North American series

Penile intraepithelial neoplasia (PeIN) is classified as human papillomavirus (HPV)- and non-HPV-related. This classification is associated with distinct morphologic subtypes. The natural history and prognosis of PeIN subtypes are not well known. This study aims to evaluate clinicopathological features, HPV status, and outcome of PeIN subtypes. Eighty-two lesions from 64 patients with isolated PeIN were retrospectively reviewed. Mean age was 59 years. Lesions were multicentric in 34% of patients and affected glans (33%), shaft (26%), and foreskin (20%). Histologically, 22% of patients had coexisting lesions, classified as hybrid and mixed. HPV-related PeIN (97%) included basaloid (59%), warty (8%), warty-basaloid (8%), hybrid (19%) and mixed (3%) types. P16 and HPV positivity occurred in 99% and 82% of lesions, respectively. HPV 16 was more common in basaloid PeIN. Multiple genotypes were detected in 35%, more commonly in hybrid PeIN (P = 0.051). Positive margins occurred in 63% of excisions. PeIN recurred in 48% of excisions and 30% of overall repeated procedures, and progression to invasive carcinoma occurred in 2%. At follow-up, 86% of patients had no evidence of disease and 12% were alive with disease. Lichen sclerosus occurred in non-HPV and HPV-related PeIN (100% and 47%).In conclusion, HPV-related and, more specifically basaloid PeIN were the predominant types and preferentially associated with HPV 16. While PeIN had a high recurrence rate, there was a slow and infrequent progression to invasive or metastatic carcinoma with multimodal treatments. Additional studies are needed to understand biology and natural history of PeIN.

Prostatic Malakoplakia: Clinicopathologic Assessment of a Multi-institutional Series of 49 Patients

Prostatic MP is rare, with only case reports and small series (<5 patients) available in the literature. In this study we analyzed an international multi-institutional series of 49 patients with prostatic MP to better define its clinicopathologic features. The median age was 67 years, and the median serum PSA was 7.5 ng/mL. MP was clinically manifest in most cases (28/45 patients with data available, 62%). Of 43 patients with detailed clinical history available, 21 (49%) had concurrent or metachronous malignancies (including prostate cancer). Diabetes or insulin resistance was present in 11 patients (26%). Additionally, 3 patients had a history of solid organ transplantation and 1 had HIV. Of note, 6/34 patients (18%) without concurrent prostate cancer had an abnormal digital rectal examination or PIRADS ≥ 4 lesions on MRI. The initial diagnosis was made on core biopsies (25/49, 51%), transurethral resection specimens (12/49, 24%), radical prostatectomies (10/49, 20%), Holmium-laser enucleation (1/49, 2%) and cystoprostatectomy (1/49, 2%). Tissue involvement was more commonly diffuse or multifocal (40/49, 82%). Von Kossa and Periodic acid-Schiff stains were positive in 35/38 (92%) and 26/27 lesions (96%), respectively. Of note, 2 cases were received in consultation by the authors with a preliminary diagnosis of mesenchymal tumor/tumor of the specialized prostatic stroma. In conclusion, the present study, which is the largest to date, suggests that prostatic MP often manifests with signs and symptoms that may mimic those of prostate cancer in a subset of patients. Moreover, MP may be found incidentally in patients with concurrent prostate cancer.

Adult Wilms Tumor: Genetic Evidence of Origin of a Subset of Cases From Metanephric Adenoma

The genetics of nephroblastoma (Wilms tumor) occurring in adults is largely unknown, as studies have largely been limited to isolated case reports. We, therefore, studied 14 adult Wilms tumors for genetic alterations, using expanded targeted sequencing on 11 cases. The patients ranged from 17 to 46 years of age (mean and median, 31 y), and there were 8 males and 6 females. Five Wilms tumors harbored BRAF V600E mutations. All of these had better-differentiated areas identical to metanephric adenoma, as has previously been described. In 3 such cases, microdissection studies revealed that the BRAF V600E mutation was present in both the metanephric adenoma and Wilms tumor areas; however, additional genetic alterations (including TERT promoter mutations in 2 cases, ASLX1/ATR mutations in 1 other case) were limited to the Wilms tumor component. These findings suggest that the Wilms tumor developed from the metanephric adenoma. Other adult Wilms tumors harbored genetic alterations previously reported in the more common pediatric Wilms tumors, including WT1 mutations (2 cases), ASLX1 mutations (3 additional cases), NSD2 mutation (1 additional case), and 11p loss (3 cases). In summary, a significant subset of adult Wilms tumors (specifically those of epithelial type with differentiated areas) harbor targetable BRAF V600E mutations and appear to arise from metanephric adenomas as a consequence of additional acquired genetic alterations. Other adult Wilms tumors often harbor genetic alterations found in their more common pediatric counterparts, suggesting at least some similarities in their pathogenesis.

Poorly Differentiated Scrotal Carcinoma With Apocrine Immunophenotype

ABSTRACT

Cutaneous carcinoma of the scrotum is rare with the most common type being squamous cell carcinoma. Here, we report 6 cases of poorly differentiated carcinoma with apocrine immunophenotype. Mean age at presentation was 68 years (range: 31-91 years). Clinical presentation included eczematous rash over mass, scrotal cyst, ulcerated mass, and mass. Tumor size ranged from 1.2 to 5.5 cm (average 2.5 cm). The tumors were solid with involvement of the dermis/hypodermis and composed of cords and nests of eosinophilic cells displaying nuclei with prominent nucleoli and surrounded by desmoplastic stroma. Focal squamous differentiation was evident in one case (17%). An intraductal component was seen in one case (17%). Pagetoid spread in the epidermis was seen in 3 cases. There was no morphologic evidence of apocrine differentiation. By immunohistochemistry, the tumor cells were positive for GCDFP-15 (n = 6/6), GATA3 (n = 6/6), CK7 (n = 5/5), AR (n = 4/4), and mammaglobin (n = 3/5). Five (83%) patients had metastases at diagnosis. Treatment included wide local excisions and inguinal lymph node dissection, followed by chemotherapy (gemcitabine, carboplatin; n = 3), trastuzumab/Lupron (n = 1), tamoxifen/Arimidex (n = 1), and radiotherapy (n = 1). Two patients (40%) were dead of disease, less than 2 years from diagnosis. Four patients developed metastases to lymph nodes, liver, bones, and lungs. Molecular analysis (n = 2) detected a HER-2 mutation in one and microsatellite instability in another. Although the presence of an intraepidermal pagetoid component could hint toward the diagnosis of invasive extramammary Paget disease, tumors without an intraepidermal component could be diagnostically challenging given the lack of morphologic evidence of apocrine differentiation.

Intraductal Adenocarcinoma of the Prostate With Cribriform or Papillary Ductal Morphology: Rare Biopsy Cases Lacking Associated Invasive High-grade Carcinoma

Prostatic duct adenocarcinoma, characterized by pseudostratified columnar epithelium, has historically been considered invasive carcinoma, although it may commonly have an intraductal component. Usual (acinar) intraductal carcinoma of the prostate (IDC-P) is a noninvasive high-risk lesion typically associated with high-grade, high-stage prostate cancer. Whereas there have been rare biopsy studies of pure acinar IDC-P or IDC-P associated with only low-grade carcinoma, there have been no analogous series of IDC-P with cribriform or papillary ductal morphology on biopsy unassociated with invasive high-grade carcinoma. We identified 14 patients with biopsies showing IDC-P with ductal morphology, defined as prostatic duct adenocarcinoma confined to glands/ducts with immunohistochemically proven retention of basal cells. Our series includes 12 patients with pure IDC-P and 2 patients with concurrent low-volume Grade Group 1 invasive cancer in unassociated cores. Three patients underwent radical prostatectomy: 2/3 had high-grade cancer in their resection specimen (Grade Group 3, Grade Group 5), including 1 with advanced stage and nodal metastases; 1/3 had Grade Group 1 organ-confined carcinoma and spatially distinct IDC-P with ductal morphology. Five men had only follow-up biopsies: 2/5 had cancer (Grade Group 2, Grade Group 4); 1/5 had IDC-P (on 2 repeat biopsies); and 2/5 had benign transurethral resection of the prostate. In all 5 cases with invasive cancer, the invasive portion was comprised purely of acinar morphology; no invasive ductal component was identified. Five patients did not have follow-up biopsies and were treated with radiation therapy±androgen deprivation. One patient had no follow-up information. In an analogous situation to acinar IDC-P, we propose that rarely there is a precursor form of ductal adenocarcinoma that can exist without concurrent invasive high-grade carcinoma and propose the term "IDC-P with ductal morphology," consistent with the terminology for acinar prostate adenocarcinoma. Until more evidence is accumulated, we recommend reporting and treating patients with IDC-P with ductal morphology in a manner analogous to those with acinar IDC-P. As with pure IDC-P with acinar morphology, we would also recommend not grading pure IDC-P with ductal morphology. Finally, we propose a new addition to the diagnostic criteria of IDC-P to include intraductal lesions with ductal morphology consisting of papillary fronds or cribriform lesions lined by cytologically atypical pseudostratified epithelium.

Multiphoton Microscopy for Identifying Collagen Signatures Associated with Biochemical Recurrence in Prostate Cancer Patients

Prostate cancer is a heterogeneous disease that remains dormant for long periods or acts aggressively with poor clinical outcomes. Identifying aggressive prostate tumor behavior using current glandular-focused histopathological criteria is challenging. Recent evidence has implicated the stroma in modulating prostate tumor behavior and in predicting post-surgical outcomes. However, the emergence of stromal signatures has been limited, due in part to the lack of adoption of imaging modalities for stromal-specific profiling. Herein, label-free multiphoton microscopy (MPM), with its ability to image tissue with stromal-specific contrast, is used to identify prostate stromal features associated with aggressive tumor behavior and clinical outcome. MPM was performed on unstained prostatectomy specimens from 59 patients and on biopsy specimens from 17 patients with known post-surgery recurrence status. MPM-identified collagen content, organization, and morphological tumor signatures were extracted for each patient and screened for association with recurrent disease. Compared to tumors from patients whose disease did not recur, tumors from patients with recurrent disease exhibited higher MPM-identified collagen amount and collagen fiber intensity signal and width. Our study shows an association between MPM-identified stromal collagen features of prostate tumors and post-surgical disease recurrence, suggesting their potential for prostate cancer risk assessment.

The Genitourinary Pathology Society Update on Classification of Variant Histologies, T1 Substaging, Molecular Taxonomy, and Immunotherapy and PD-L1 Testing Implications of Urothelial Cancers

The Genitourinary Pathology Society (GUPS) undertook a critical review of the recent advances in bladder cancer focusing on important topics of high interest for the practicing surgical pathologist and urologist. This review represents the second of 2 manuscripts ensuing from this effort. Herein, we address the effective reporting of bladder cancer, focusing particularly on newly published data since the last 2016 World Health Organization (WHO) classification. In addition, this review focuses on the importance of reporting bladder cancer with divergent differentiation and variant (subtypes of urothelial carcinoma) histologies and the potential impact on patient care. We provide new recommendations for reporting pT1 staging in diagnostic pathology. Furthermore, we explore molecular evolution and classification, emphasizing aspects that impact the understanding of important concepts relevant to reporting and management of patients.

The Genitourinary Pathology Society Update on Classification and Grading of Flat and Papillary Urothelial Neoplasia With New Reporting Recommendations and Approach to Lesions With Mixed and Early Patterns of Neoplasia

The Genitourinary Pathology Society (GUPS) undertook a critical review of the recent advances in bladder neoplasia with a focus on issues relevant to the practicing surgical pathologist for the understanding and effective reporting of bladder cancer, emphasizing particularly on the newly accumulated evidence post-2016 World Health Organization (WHO) classification. The work is presented in 2 manuscripts. Here, in the first, we revisit the nomenclature and classification system used for grading flat and papillary urothelial lesions centering on clinical relevance, and on dilemmas related to application in routine reporting. As patients of noninvasive bladder cancer frequently undergo cystoscopy and biopsy in their typically prolonged clinical course and for surveillance of disease, we discuss morphologies presented in these scenarios which may not have readily applicable diagnostic terms in the WHO classification. The topic of inverted patterns in urothelial neoplasia, particularly when prominent or exclusive, and beyond inverted papilloma has not been addressed formally in the WHO classification. Herein we provide a through review and suggest guidelines for when and how to report such lesions. In promulgating these GUPS recommendations, we aim to provide clarity on the clinical application of these not so uncommon diagnostically challenging situations encountered in routine practice, while also importantly advocating consistent terminology which would inform future work.

Novel, emerging and provisional renal entities: The Genitourinary Pathology Society (GUPS) update on renal neoplasia

The Genitourinary Pathology Society (GUPS) undertook a critical review of the recent advances in renal neoplasia, particularly focusing on the newly accumulated evidence post-2016 World Health Organization (WHO) classification. In the era of evolving histo-molecular classification of renal neoplasia, morphology is still key. However, entities (or groups of entities) are increasingly characterized by specific molecular features, often associated either with recognizable, specific morphologies or constellations of morphologies and corresponding immunohistochemical profiles. The correct diagnosis has clinical implications leading to better prognosis, potential clinical management with targeted therapies, may identify hereditary or syndromic associations, which may necessitate appropriate genetic testing. We hope that this undertaking will further facilitate the identification of these entities in practice. We also hope that this update will bring more clarity regarding the evolving classification of renal neoplasia and will further reduce the category of "unclassifiable renal carcinomas/tumors". We propose three categories of novel entities: (1) "Novel entity", validated by multiple independent studies; (2) "Emerging entity", good compelling data available from at least two or more independent studies, but additional validation is needed; and (3) "Provisional entity", limited data available from one or two studies, with more work required to validate them. For some entities initially described using different names, we propose new terminologies, to facilitate their recognition and to avoid further diagnostic dilemmas. Following these criteria, we propose as novel entities: eosinophilic solid and cystic renal cell carcinoma (ESC RCC), renal cell carcinoma with fibromyomatous stroma (RCC FMS) (formerly RCC with leiomyomatous or smooth muscle stroma), and anaplastic lymphoma kinase rearrangement-associated renal cell carcinoma (ALK-RCC). Emerging entities include: eosinophilic vacuolated tumor (EVT) and thyroid-like follicular renal cell carcinoma (TLFRCC). Finally, as provisional entities, we propose low-grade oncocytic tumor (LOT), atrophic kidney-like lesion (AKLL), and biphasic hyalinizing psammomatous renal cell carcinoma (BHP RCC).

The 2019 Genitourinary Pathology Society (GUPS) White Paper on Contemporary Grading of Prostate Cancer

CONTEXT.—

Controversies and uncertainty persist in prostate cancer grading.

OBJECTIVE.—

To update grading recommendations.

DATA SOURCES.—

Critical review of the literature along with pathology and clinician surveys.

CONCLUSIONS.—

Percent Gleason pattern 4 (%GP4) is as follows: (1) report %GP4 in needle biopsy with Grade Groups (GrGp) 2 and 3, and in needle biopsy on other parts (jars) of lower grade in cases with at least 1 part showing Gleason score (GS) 4 + 4 = 8; and (2) report %GP4: less than 5% or less than 10% and 10% increments thereafter. Tertiary grade patterns are as follows: (1) replace "tertiary grade pattern" in radical prostatectomy (RP) with "minor tertiary pattern 5 (TP5)," and only use in RP with GrGp 2 or 3 with less than 5% Gleason pattern 5; and (2) minor TP5 is noted along with the GS, with the GrGp based on the GS. Global score and magnetic resonance imaging (MRI)-targeted biopsies are as follows: (1) when multiple undesignated cores are taken from a single MRI-targeted lesion, an overall grade for that lesion is given as if all the involved cores were one long core; and (2) if providing a global score, when different scores are found in the standard and the MRI-targeted biopsy, give a single global score (factoring both the systematic standard and the MRI-targeted positive cores). Grade Groups are as follows: (1) Grade Groups (GrGp) is the terminology adopted by major world organizations; and (2) retain GS 3 + 5 = 8 in GrGp 4. Cribriform carcinoma is as follows: (1) report the presence or absence of cribriform glands in biopsy and RP with Gleason pattern 4 carcinoma. Intraductal carcinoma (IDC-P) is as follows: (1) report IDC-P in biopsy and RP; (2) use criteria based on dense cribriform glands (>50% of the gland is composed of epithelium relative to luminal spaces) and/or solid nests and/or marked pleomorphism/necrosis; (3) it is not necessary to perform basal cell immunostains on biopsy and RP to identify IDC-P if the results would not change the overall (highest) GS/GrGp part per case; (4) do not include IDC-P in determining the final GS/GrGp on biopsy and/or RP; and (5) "atypical intraductal proliferation (AIP)" is preferred for an intraductal proliferation of prostatic secretory cells which shows a greater degree of architectural complexity and/or cytological atypia than typical high-grade prostatic intraepithelial neoplasia, yet falling short of the strict diagnostic threshold for IDC-P. Molecular testing is as follows: (1) Ki67 is not ready for routine clinical use; (2) additional studies of active surveillance cohorts are needed to establish the utility of PTEN in this setting; and (3) dedicated studies of RNA-based assays in active surveillance populations are needed to substantiate the utility of these expensive tests in this setting. Artificial intelligence and novel grading schema are as follows: (1) incorporating reactive stromal grade, percent GP4, minor tertiary GP5, and cribriform/intraductal carcinoma are not ready for adoption in current practice.

Verrucous Squamous Hyperplasia of the Urinary Bladder

CONTEXT.—

There is scant literature describing verrucous squamous hyperplasia of the urinary bladder.

OBJECTIVE.—

To investigate the possible association between verrucous squamous hyperplasia and carcinoma.

DESIGN.—

The case files of the senior author were searched for cases of verrucous squamous hyperplasia diagnosed between August 2010 and February 2021. Cases with available material were tested for in situ hybridization with human papillomavirus, and cases with available material unassociated with carcinoma underwent immunohistochemistry for p53.

RESULTS.—

We gathered a series of 23 cases, the largest to date. Eleven cases were associated with carcinoma at diagnosis. Of the 7 cases unassociated with carcinoma in which follow-up was available, 1 patient (14.3%) was given a clinical diagnosis of carcinoma with recommended cystectomy, 2 (28.6%) had benign diagnoses, and 4 (57.1%) were dead not from disease. Of the 13 cases with available material, 13 (100%) were negative for human papillomavirus by high-risk in situ hybridization.

CONCLUSIONS.—

Based on the small number of cases with limited follow-up, it is unclear whether verrucous squamous hyperplasia represents a precursor lesion or simply a high-risk association. Until more evidence is accumulated, patients with verrucous squamous hyperplasia of the urinary bladder should receive close clinical follow-up.

Pediatric Mesothelioma With ALK Fusions: A Molecular and Pathologic Study of 5 Cases

Pediatric mesotheliomas are rare and their pathogenesis remains undefined. In this study, we report 5 cases of malignant mesothelioma in children, characterized by fusions involving the anaplastic lymphoma kinase (ALK) gene. Four cases occurred in females involving the abdominal cavity and were characterized by a pure epithelioid morphology. The fifth arose in the tunica vaginalis of a 15-year-old male and displayed a biphasic epithelioid-sarcomatoid phenotype. All cases demonstrated the classic morphologic and immunohistochemical features of malignant mesothelioma, including tubulopapillary architecture and cuboidal epithelioid cells with eosinophilic cytoplasm and uniform nuclei with vesicular chromatin. Immunohistochemically, all cases showed labeling for ALK, cytokeratins, WT1, and calretinin, while lacking expression of adenocarcinoma immunomarkers. Four cases demonstrated weak-moderate labeling for PAX8 protein, which resulted in diagnostic challenges with primary peritoneal serous carcinoma. The ALK genetic abnormalities were investigated by a combination of molecular methods. Archer FusionPlex was performed in 2 cases, showing fusions between ALK with either STRN or TPM1 genes, resulting in a transcript that retained the ALK kinase domain. One case was further studied by DNA targeted sequencing, but no additional genetic alterations were observed. In 1 case, cytogenetic analysis showed the presence of a t(2;15)(p23;q22) and fluorescence in situ hybridization confirmed the ALK gene break-apart. In the remaining 2 cases, ALK gene rearrangements were demonstrated by fluorescence in situ hybridization. Unlike adult mesotheliomas, which are tightly linked to asbestos exposure, often show loss of BAP1 expression and have complex karyotypes, ALK-rearranged mesothelioma appears to be similar to other fusion-positive mesotheliomas, such as those harboring EWSR1/FUS-ATF1 fusions, sharing significant morphologic overlap, occurring in young patients and displaying a simple, translocation-driven genetic profile.

Noninvasive low-grade papillary urothelial carcinoma with degenerative nuclear atypia: a grading pitfall

Noninvasive low-grade papillary urothelial carcinoma is a papillary neoplasm with orderly appearance and mild nuclear pleomorphism. Some cases show significant nuclear pleomorphism with degenerative atypia leading to grading difficulties. A retrospective review of the pathology files identified 16 cases diagnosed as noninvasive low-grade papillary urothelial carcinoma with degenerative atypia. Fifteen cases were consults. The average age was 46 years (range 19-78). The average size was 1.7 cm (range: 0.3-3.5). The submitting diagnoses in consults were noninvasive high-grade papillary urothelial carcinoma (n = 6), condyloma (n = 1), atypical papillary lesion (n = 1), prominent umbrella cells (n = 1), and not given (n = 6). Ki-67 proliferation rate was <5% in 10 of 10 cases (100%), and the cells with large atypical nuclei were negative. Microscopically, there were scattered cells with nuclei larger than 5 times the size of stromal lymphocytes but displayed smudgy chromatin and occasional multinucleation and intranuclear vacuoles. Next-generation sequencing identified the following mutations: HRAS (n = 4), FGFR3 (n = 3), KRAS (n = 3), BRAF (n = 1), PDGFRA (n = 1), and PIK3CA (n = 1). Other deleterious mutations were identified, but none in genes characteristic of high-grade tumors. Follow-up was available in 6 patients (median 32 months). One patient recurred with a noninvasive low-grade papillary urothelial carcinoma 20 months after the index case. All the remaining patients had no evidence of disease at the last follow-up. No patient died or had disease progression. The combination of preservation of polarity, low mitotic activity, Ki-67 <5% with the larger atypical nuclei negative for Ki-67, along with nuclear atypia that is degenerative are features used to classify these tumors as low grade.

Nested Variant of Urothelial Carcinoma Is a Luminal Bladder Tumor With Distinct Coexpression of the Basal Marker Cytokeratin 5/6

OBJECTIVES

The nested variant of urothelial carcinoma (NVUC) is a rare bladder tumor that may possess a luminal molecular phenotype. We sought to determine whether a small immunohistochemical (IHC) panel using common surrogates for molecular phenotypes would reliably classify a cohort of pure NVUC cases.

METHODS

IHC staining with a panel composed of markers for basal subtypes (CK5/6, CK14) and luminal subtypes (FOXA1, GATA3) was performed on pure small NVUC cases (n = 23) and 5 large NVUC cases (n = 5). Scoring of IHC stains was performed semiquantitatively. Individual cases were analyzed using previously reported IHC-based surrogates for molecular subtype.

RESULTS

The phenotype of NVUC was classified as luminal from 60.1% (FOXA1+/CK5/6-) to 100% (GATA3+/CK14-) of cases using composite phenotypes. No cases possessed a basal or squamous cell carcinoma-like phenotype. The majority of small NVUC cases (69.5%) showed subset CK5/6 expression distinctly localized to the basal layers of tumor cell nests. Intratumoral heterogeneity was also noted in CK5/6 (21.7% of small NVUC cases) but no other markers.

CONCLUSIONS

NVUC appears to express markers of both basal and luminal bladder tumors. Definitive gene expression profiling may be valuable to further characterize this unique histologic variant.

Plasma cell neoplasms of the bladder: a series of 9 cases

From 2009 to 2017, we identified 9 cases of plasma cell neoplasms on biopsies of the bladder in patients without a history of plasma cell myeloma or transplantation (6 men and 3 women). Four of the nine showed amyloid deposition, of which one additionally revealed a clear cell adenocarcinoma of the bladder. Follow-up was obtained in 7 cases. Of 3 cases (including 2 with amyloid) for which electrophoresis and immunofixation results were obtained, the 2 amyloid cases showed evidence of serum or urine paraproteins: serum IgM kappa in a patient with kappa light chain-restricted plasma cell neoplasm and urine IgA lambda in a patient with lambda light chain-restricted plasma cell neoplasm. By way of contrast, 1 case with kappa light chain-restricted plasma cell neoplasm in the absence of amyloid showed no serum monoclonal protein. Bone marrow biopsy results were obtained in the 2 amyloid cases revealing a population of 5% or less plasma cells with no assessment of clonality and, thus, were not diagnostic of plasma cell myeloma. In congruence, the 2 amyloid cases also showed no radiologic evidence of systemic plasma cell myeloma. One patient with plasma cell neoplasm only received chemotherapy and radiation without subsequent biopsies; one patient with plasma cell neoplasm, amyloid, and clear cell adenocarcinoma received radiation with an absence of neoplastic disease on subsequent biopsies. In addition, no evidence of systemic amyloid was found in the cases with bladder amyloidosis. Plasma cell neoplasms of the bladder, with and without amyloid deposition, are rare; this is the first known case series. In 7 cases with follow-up, plasma cell myeloma did not appear to manifest in a 1- to 127-month follow-up. However, paraproteins were identified on further testing in 2 cases with amyloid. Although bladder plasma cell neoplasms with and without amyloid tend to have a favorable prognosis in short-term follow-up, our study supports the need for additional workup for systemic disease, particularly in those with concurrent amyloidosis.

Genomic and phenotypic heterogeneity in prostate cancer

From a clinical, morphological and molecular perspective, prostate cancer is a heterogeneous disease. Primary prostate cancers are often multifocal, having topographically and morphologically distinct tumour foci. Sequencing studies have revealed that individual tumour foci can arise as clonally distinct lesions with no shared driver gene alterations. This finding demonstrates that multiple genomically and phenotypically distinct primary prostate cancers can be present in an individual patient. Lethal metastatic prostate cancer seems to arise from a single clone in the primary tumour but can exhibit subclonal heterogeneity at the genomic, epigenetic and phenotypic levels. Collectively, this complex heterogeneous constellation of molecular alterations poses obstacles for the diagnosis and treatment of prostate cancer. However, advances in our understanding of intra-tumoural heterogeneity and the development of novel technologies will allow us to navigate these challenges, refine approaches for translational research and ultimately improve patient care.

Adverse histology, homozygous loss of CDKN2A/B, and complex genomic alterations in locally advanced/metastatic renal mucinous tubular and spindle cell carcinoma

Mucinous tubular and spindle cell carcinoma (MTSCC) is a rare subtype of renal cell carcinoma with characteristic histologic features and chromosomal alterations. Although typically indolent, a small subset of cases has been reported to exhibit aggressive clinical behavior. We retrospectively identified 33 patients with MTSCC, consisting of 10 cases of locally advanced/metastatic MTSCC (pT3 or N1 or M1) and 23 kidney-confined MTSCC (pT1/T2) without disease recurrence or progression. Utilizing a single-nucleotide polymorphism array and a targeted next-generation sequencing platform, we examined genome-wide molecular alterations in 24 cases, including 11 available samples from 8 patients with locally advanced/metastatic MTSCC. Ten patients with locally advanced/metastatic MTSCC were 8 females (80%) and 2 males (20%). At nephrectomy, 7 of these 10 cases (70%) were pT3 or pN1 while the remaining 3 (30%) were pT1/T2. Eight patients (80%) developed metastases and common sites included lymph node (4, 40%), bone (4, 40%), and retroperitoneum (3, 30%). Four patients died of disease (40%) during follow-up. Locally advanced/metastatic MTSCCs shared typical MTSCC genomic profiles with loss of chromosomes 1, 4, 6, 8, 9, 13, 14, 15, and 22, while some exhibited additional complex genomic alterations, most frequently a relative gain of 1q (7/8). Homozygous loss of CDKN2A/B was observed in 3 (38%) locally advanced/metastatic MTSCCs. Tumor necrosis, solid nested/sheet pattern, irregular trabecular/single-file infiltration in a desmoplastic stroma, lymphovascular space invasion, and increased mitotic activity were associated with locally advanced/metastatic MTSCCs (all p < 0.05). Our findings reveal that MTSCCs with aggressive clinical behavior have progressed through clonal evolution; CDKN2A/B deletion and additional complex genomic abnormalities may contribute to this process. Recognizing the morphologic presentation of high-grade MTSCC and evaluating adverse histologic features seen in these tumors can help establish a definitive diagnosis and stratify patients for treatment and prognostication.

Well-differentiated neuroendocrine tumors of the lower urinary tract: biologic behavior of a rare entity

The spectrum of neuroendocrine (NE) tumors in the genitourinary tract ranges from the aggressive large and small cell carcinomas to the often benign paraganglioma and well-differentiated neuroendocrine tumor (WD-NET). At least 15 pure lower urinary tract (LUT) WD-NETs have been described. Owing to the rarity of WD-NET in the LUT and the limited number of reported cases, a better definition of their biologic long-term behavior is warranted. Herein, we aim to describe 10 new cases of WD-NET arising in the LUT and expand on follow-up findings. Ten consultation cases were identified and included 6 men and 4 women who ranged from 45 to 73 years of age. Seven cases arose in the bladder with one located in the bladder neck, 1 arose in the prostatic urethra, 1 arose in the female urethra, and 1 arose in the left ureteral orifice. All lesions were confined to the lamina propria, and tumor architecture was pseudoglandular in all cases. Associated cystitis cystica et glandularis was identified in 5 cases; urothelial papilloma and florid von Brunn's nests were found in 2 additional cases. Immunohistochemical staining for synaptophysin and chromogranin was diffusely positive in 9 cases and focal in 1 case, and the Ki-67 proliferation index was 5% or less in all tumors. Follow-up ranged from 37 to 137 months (mean = 82; median = 77), and there was no evidence of residual disease or recurrence in any of the 10 patients during the follow-up period.

A Comparison of Genitourinary Society Pathology and International Society of Urological Pathology Prostate Cancer Guidelines

In 2019, the Genitourinary Pathology Society (GUPS) and International Society of Urological Pathology (ISUP) held their own consensus conferences on prostate cancer grading and reporting, with separately published manuscripts. The majority of GUPS and ISUP grading recommendations are compatible, but for some issues there is a lack of concordance or recommendations between the societies. As a result, both in practice and in research, these differences may manifest in difficulties when comparing pathology reports or data.

Gastrointestinal Malakoplakia: Clinicopathologic Analysis of 26 Cases

Malakoplakia is an inflammatory process related to defective macrophage response to bacterial infection. To further characterize the clinicopathologic manifestations of gastrointestinal malakoplakia, 26 cases were identified from 6 institutions. Hematoxylin and eosin-stained slides and available stains were reviewed, and pertinent clinicopathologic features analyzed. Sixteen patients were women (62%). Mean patient age was 64 (range: 24 to 83). Sites included the colorectum (n=23), appendix (n=1), and stomach (n=2). Clinical indications for tissue procurement included screening (n=14), tumor resection (n=5), diarrhea (n=1), adenoma surveillance (n=1), ulcerative colitis flare (n=1), abdominal pain (n=1), and appendicitis (1). All cases featured histiocytes with abundant, pale, eosinophilic cytoplasm focally containing Michaelis-Gutmann bodies. The process frequently involved the mucosa (n=19), with architectural distortion in 13 cases. Lymphoid aggregates were present in 18 cases, which were prominent or obscuring in 11 (all colon biopsies) and provoked concern for lymphoma in 2. Associated findings included adenocarcinoma (n=5), adenoma (n=2), gastric hyperplastic polyps (n=1), chemical gastritis (n=1), collagenous colitis (n=1), and active chronic colitis (n=2). In cases with available stains, Michaelis-Gutman bodies were highlighted by Periodic Acid-Schiff with diastase, Von Kossa, and iron stains. Although 2 cases were positive for Tropheryma whipplei antibody, no T. whipplei transcripts were detected on real-time polymerase chain reaction. All patients with available follow-up are alive and well with no additional instances of malakoplakia. Malakoplakia of the gastrointestinal tract is a benign, incidental finding. Although histologic features in the stomach and colon resections are similar to those at other sites, exuberant lymphocytic response in colon biopsies and immunoreactivity with T. whippleii antibody may provoke initial confusion and lead to unnecessary time and resource investment.

PIN-like ductal carcinoma of the prostate has frequent activating RAS/RAF mutations

AIMS

Prostatic intraepithelial neoplasia-like (PIN-like) ductal carcinoma is a rare tumour characterised by often cystically dilated glands architecturally resembling high-grade PIN, but lacking basal cells. These tumours are frequently accompanied by grade group 1 acinar cancer and behave relatively indolently. In contrast, conventional ductal adenocarcinoma of the prostate is an aggressive variant comparable to grade group 4 acinar cancer. Here, we used targeted next-generation sequencing to molecularly profile PIN-like ductal carcinoma cases at radical prostatectomy.

METHODS AND RESULTS

Five PIN-like ductal carcinoma samples at radical prostatectomy with sufficient tumour tissue available were analysed for genomic alterations by targeted next-generation sequencing using the Johns Hopkins University (JHU) solid tumour panel. DNA was captured using SureSelect for 640 genes and sequenced on the Illumina HiSeq platform. Three of five (60%) of the PIN-like ductal carcinomas showed activating mutations in the RAS/RAF pathways, which are extraordinarily rare in conventional primary prostate carcinoma (<3% of cases), including an activating hot-spot BRAF mutation (p.K601E), an activating hot-spot mutation in HRAS (p.Q61K) and an in-frame activating deletion in BRAF (p.T488_Q493delinsK). An additional two cases lacked BRAF or HRAS mutations, but harboured in-frame insertions of uncertain significance in MAP2K4 and MAP3K6. One case had sufficient acinar tumour for sequencing, and showed a similar molecular profile as the concurrent PIN-like ductal carcinoma, suggesting a clonal relationship between the two components.

CONCLUSIONS

PIN-like ductal carcinoma represents a molecularly unique tumour, enriched for potentially targetable oncogenic driver mutations in the RAS/RAF/MAPK pathway. This molecular profile contrasts with that of conventional ductal adenocarcinoma, which is typically enriched for pathogenic mutations in the mismatch repair (MMR) and homologous recombination (HR) DNA repair pathways.