Prostatic carcinoma with abundant xanthomatous cytoplasm. Foamy gland carcinoma

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.

Patient with prostatic adenocarcinoma with plasmacytoid features and an aberrant immunohistochemical phenotype diagnosed by biopsy and a mini-review of plasmacytoid features in the genitourinary system: A case report

Prostate cancer is one of the most commonly diagnosed malignancies in men. Most of these tumors are adenocarcinomas. Plasmacytoid is a rare variant of adenocarcinoma described by previous studies in the genitourinary system and is characterized by the plasmacytoid appearance of tumor cells with abundant cytoplasm and abnormally placed hyperchromatic nuclei. However, to the best of our knowledge, plasmacytoid adenocarcinoma has rarely been described in the prostate. This report describes a new case of plasmacytoid adenocarcinoma of the prostate diagnosed by biopsy and summarizes the known literature on plasmacytoid features in the genitourinary system. A 62-year-old male patient presented to the hospital with urinary retention, hematuria, weakness and weight loss. The digital rectal examination revealed an irregular enlargement. Laboratory findings showed elevated levels of prostate specific antigen (PSA; 43.6 ng/ml). Transrectal ultrasound showed invasion of the right seminal vesicle. Prostate tumor core biopsies were collected and sent for diagnosis. Histological examination revealed a high-grade prostatic adenocarcinoma Gleason score of 5+5 (total score 10). The tumor cells had a plasmacytoid appearance with abundant cytoplasm and abnormally placed hyperchromatic nuclei. The immunohistochemical phenotype was characterized by abundant positivity for cytokeratin (CK)AE1/AE3 and PSA. By contrast, tumor cells were negative for p63, CK 34BE12 and GATA binding protein 3 (urothelial markers), synaptophysin (neuroendocrine marker). Tumor cells were also negative for E-cadherin, which is particularly indicative of CDH1 alterations. To the best of our knowledge, this is the first description of a plasmacytoid adenocarcinoma of the prostate diagnosed by biopsy, showing an irregular immunophenotype that may indicate somatic CDH1 alterations. The presentation of a novel rare variant of prostatic carcinoma that differs from other neoplasms of the genitourinary system may contribute to an improved understanding of this uncommonly found histological pattern that may also be mandatory due to the clinical and prognostic implications of this diagnosis.

False-Negative Histopathologic Diagnosis of Prostatic Adenocarcinoma

Context.—

Histopathologic diagnosis of adenocarcinoma of the prostate is based on light-microscopic examination of hematoxylin-eosin–stained tissue sections. Multiple factors, including preanalytic and analytic elements, affect the ability of the pathologist to accurately diagnose prostatic adenocarcinoma. False-negative diagnosis, that is, failure to diagnose prostatic adenocarcinoma, may have serious clinical consequences. It is important to delineate and understand those factors that may affect and cause histopathologic false-negative diagnoses of prostatic adenocarcinoma.

Objectives.—

To review common factors involved in histopathologic underdiagnosis of prostatic adenocarcinoma, including the following: (1) tissue processing and sectioning artifacts, (2) minimal adenocarcinoma, (3) deceptively benign appearing variants of acinar adenocarcinoma, (4) single cell adenocarcinoma, and (5) treatment effects.

Data Sources.—

Data sources included published, peer-reviewed literature and personal experiences of the senior author.

Conclusions.—

Knowledge of the reasons for histopathologic false-negative diagnosis of adenocarcinoma of the prostate is an important component in the diagnostic assessment of prostate tissue sections. Diagnostic awareness of the histomorphologic presentations of small (minimal) adenocarcinoma; deceptively benign appearing variants including atrophic, foamy gland, microcystic, and pseudohyperplastic variants; single cell carcinoma; and treatment effects is critical for establishment of a definitive diagnosis of adenocarcinoma and the prevention of false-negative diagnoses of prostate cancer.

Case - Foamy, high-grade prostatic intraepithelial neoplasia: A false positive for prostate cancer on multiparametric magnetic resonance imaging?

The introduction of multiparametric magnetic resonance imaging (mpMRI) of the prostate, and specifically the introduction of diffusion-weighted imaging (DWI), has significantly impacted the diagnosis of prostate cancer and the management of clinically localized prostate cancer. Indeed, its localizing ability has now opened up opportunities to target focal lesions in partial gland ablation therapy as a treatment option for localized prostate cancer. With negative predictive rates of mpMRI approaching 90% in certain series,1 mpMRI has the ability to discriminate between clinically significant intermediate-to-high-risk prostate cancer and low-risk indolent disease. However, false positives can occur. In recent studies, lesions observed on MRI were classified as tumour on targeted biopsy in 47.6% to over 94% for tumours larger than 0.5 ml in volume.2,3 Herein, we present a case of a rare non-cancer, but putatively pre-malignant prostatic histology that was found on biopsies directed at a category 5 Prostate Imaging Reporting and Data System (PIRADS) v2 lesion.

Prostate cancer grading: a decade after the 2005 modified system

This review article will cover the evolution of grading of prostate cancer from the original Gleason system in the 1960-1970s to a more patient-centric grading system proposed in 2013 from a group at Johns Hopkins Hospital, validated in 2014 by a large multi-institutional study, and subsequently accepted by the World Health Organization (WHO), College of American Pathology (CAP), and the AJCC TNM system. Covered topics include: (1) historical background; (2) 2005 and 2014 International Society of Urological Pathology Grading Conferences; (3) Description of Gleason patterns; (4) new approaches to display Gleason grades; (5) grading variants and variations of acinar adenocarcinoma; (6) reporting rules for Gleason grading reporting secondary patterns of higher grade when present to a limited extent; (7) reporting secondary patterns of lower grade when present to a limited extent; (8) reporting percentage pattern 4; (9) general applications of the Gleason grading system; (10) needle biopsy with different cores showing different grades; (11) radical prostatectomy specimens with separate tumor nodules; and (12) a new grading system for prostate cancer.

Benign mimics of prostatic adenocarcinoma

Benign mimics present either as common challenges in daily routine practice or may cause diagnostic dilemmas because some are less commonly seen and one may be less familiar in recognizing them. There are a multitude of mimics of prostatic adenocarcinoma, which may represent normal gland structures, benign proliferations, atrophic lesions, hyperplastic or metaplastic changes, and inflammatory processes. Some of them are preferentially found in certain anatomic areas of the prostate, either confined to the prostate, or outside of the gland. Various benign mimics of prostatic carcinoma may be also evaluated based on their morphologic similarity to Gleason patterns 3-5 of prostatic adenocarcinoma. Most of the mimics are easily recognizable in larger specimens, such as TUR of the prostate or radical prostatectomy specimens, but they may pose diagnostic problems when the evaluation is done on limited tissue, such as needle-core biopsies or if prostate specimens are infrequently encountered in practice. Therefore, before signing out a report with a diagnosis of prostatic carcinoma, pathologists should carefully consider and rule out the various benign lesions that may mimic carcinoma. This is particularly relevant in the current prostate biopsy practice which relies on using extended biopsy core templates. The awareness and familiarity with the characteristic features of the mimics and judicial use of additional ancillary tests, including immunohistochemistry can prevent overdiagnosis and false-positive interpretation. This review provides a contemporary update on the broad spectrum of the benign prostatic lesions that can mimic prostate adenocarcinoma, outlines their key morphologic and immunohistochemical diagnostic features, and provides a diagnostic, pattern-based approach in establishing a correct diagnosis and distinguishing them reliably from prostatic adenocarcinoma.

Prostate cancer: diagnostic criteria and role of immunohistochemistry

The diagnosis of prostate cancer is based on microscopic criteria. Presently, prostate needle biopsy interpretation can be a challenge for the pathologist due to the increased number of specimens with limited amount of suspicious glands and minimal atypia. It is critical for the pathologist to have an organized methodical approach when considering the morphological features enabling a definitive diagnosis of prostate cancer. Although several diagnostic criteria and supportive features have been advocated, only few findings are absolutely specific and diagnostic of prostate cancer. The diagnosis of prostate cancer relies on a combination of architectural and cytological features that are reviewed in detail herein. Infiltrative growth pattern, prominent nucleoli and lack of basal cells are the most useful diagnostic criteria. Perineural invasion, glomerulation and mucinous fibroplasia are pathognomonic features of prostate cancer, although uncommon on small prostate cancer foci. The role of immunohistochemistry in establishing a diagnosis of limited prostate is addressed.

Variants of acinar adenocarcinoma of the prostate mimicking benign conditions

Histological variants of acinar adenocarcinoma of the prostate may be of significance due to difficulty in diagnosis or due to differences in prognosis compared to usual acinar adenocarcinoma. The 2016 World Health Organization classification of acinar adenocarcinoma includes four variants that are deceptively benign in histological appearance, such that a misdiagnosis of a benign condition may be made. These four variants are atrophic pattern adenocarcinoma, pseudohyperplastic adenocarcinoma, microcystic adenocarcinoma, and foamy gland adenocarcinoma. They differ from usual small acinar adenocarcinoma in architectural glandular structure and/or cytoplasmic and nuclear alterations. The variants are often admixed, in variable proportions, with usual small acinar adenocarcinoma that is often Gleason pattern 3 but may be high-grade pattern 4 in a minority of cases. Atrophic pattern adenocarcinoma can be identified in a sporadic setting or after radiation or hormonal therapy. This variant is characterized by cytoplasmic volume loss and can resemble benign glandular atrophy, an extremely common benign process in the prostate. The glands of pseudohyperplastic adenocarcinoma simulate usual epithelial hyperplasia, with gland complexity that is not typical of small acinar adenocarcinoma. These complex growth configurations include papillary infoldings, luminal undulations, and branching. Microcystic adenocarcinoma is characterized by cystic dilation of prostatic glands to a size that is much more commonly observed in cystic change in benign prostatic glands. Finally, the cells in foamy gland adenocarcinoma display cytoplasmic vacuolization and nuclear pyknosis, features that can found in benign glands and macrophages. Three of the four variants (atrophic, pseudohyperplastic, and microcystic) are assigned low-grade Gleason pattern 3. Of significance, foamy gland adenocarcinoma can be Gleason pattern 3 but can also be high-grade pattern 4 or 5. Diagnostic awareness of the existence of these deceptively benign-appearing variants of acinar adenocarcinoma is essential so that an accurate diagnosis of prostate cancer may be rendered.

Histopathology of Prostate Cancer

This review focuses on histopathological aspects of carcinoma of the prostate. A tissue diagnosis of adenocarcinoma is often essential for establishing a diagnosis of prostate cancer, and the foundation for a tissue diagnosis is currently light microscopic examination of hematoxylin and eosin (H&E)-stained tissue sections. Markers detected by immunohistochemistry on tissue sections can support a diagnosis of adenocarcinoma that is primary in the prostate gland or metastatic. Histological variants of carcinoma of the prostate are important for diagnostic recognition of cancer or as clinicopathologic entities that have prognostic and/or therapeutic significance. Histological grading of adenocarcinoma of the prostate, including use of the 2014 International Society of Urological Pathology (ISUP) modified Gleason grades and the new grade groups, is one of the most powerful prognostic indicators for clinically localized prostate cancer, and is one of the most critical factors in determination of management of these patients.

Foamy gland changes in gastric-type endocervical neoplasia

Foamy gland (FG) change is a distinctive morphological alteration most widely recognised in adenocarcinomas of the prostate and pancreas, and characterised by cells showing prominent cytoplasmic microvacuolation often with deceptively bland nuclear appearances. To our knowledge, FG alteration has not been described in endocervical neoplasia. We report four patients with gastric-type endocervical neoplasms (3 invasive and 1 in situ) in which FG change was present in 30-80% of the tumour cells. The mean age was 56.5 years (range 45-66 years) and three patients, one of whom also had post-coital bleeding, had atypical glandular cells detected on cervical cytology. Three cases showed a pure gastric phenotype and benign gastric-type changes including pyloric metaplasia, tunnel clusters and/or lobular endocervical glandular hyperplasia were also present. These cases were MUC6 positive and p16 negative on immunohistochemistry while HPV was not detected. One adenocarcinoma showed a mixed histological pattern including usual-type endocervical carcinoma and gastric-type adenocarcinoma: only the latter component expressed MUC6 and this case was p16 and HPV18 positive. This report expands the morphological spectrum exhibited by gastric-type endocervical lesions and the range of anatomical sites in which neoplasms with FG features may be encountered.

The pathology of unusual subtypes of prostate cancer

There are some current literatures describing the morphologic change of prostate carcinoma variants. Some subtypes do not respond to hormone deprivation therapy, for example adenosquamous and squamous cell carcinoma (SQCC), basaloid and adenoid cystic carcinoma (ACC), small cell carcinoma (SmCC), sarcomatoid carcinoma, urothelial carcinoma; some are defined in special Gleason grade, some develop different prognosis. So, it is very important to identify these rare subtypes to avoid misdiagnosis. In this review, we aim to describe the typical clinicopathological features of the rare variants of prostate cancer, including prostate acinar adenocarcinoma morphologic variants.

Changes in prostate cancer grading: Including a new patient-centric grading system

The first structured approach to grade prostate cancer based on the underlying histological architecture was developed by Donald Gleason who in 1966 proposed a morphologic classification of prostate cancer and in 1974 demonstrated its clinical significance based on prostate cancer-specific death. Contemporarily referred to as the Gleason grading system, it has gained worldwide recognition allowing a more individualized approach to patients with prostate cancer. In 2005, the International Society of Urologic Pathology (ISUP) made the first revisions to the grading system. Subsequently, based on the new discoveries in pathologic and clinical aspects of prostate cancer, as well as the changing nature of the prostate cancer in part due to a robust screening, there was a need for experts to re-visit the approach to grade prostate cancer. In November 2014, the ISUP experts and clinical leaders in prostate cancer from 17 countries conducted a consensus conference in Chicago, IL, USA. The consensus conference defined various grade patterns and proposed the adoption of a new grading system of prostate cancer. Herein, we describe the background and rationale for the changes and provide guidelines to their clinical implementation.

Pseudohyperplastic Adenocarcinoma With Foamy Changes in Needle Prostate Biopsy and Prostatectomy

Pseudohyperplastic adenocarcinoma (PHA) with foamy changes is composed of neoplastic glands that show a cytoarchitectural combination of both neoplasms. However, none of the previously reported cases have shown typical areas of foamy or PHA. We report on the clinicopathological characteristics of 5 cases consisting predominantly of pseudohyperplastic and foamy adenocarcinomas. In several histological fields, this neoplasm mimicked hyperplastic nodules or prostatic adenosis because they showed the nodular pattern of the PHA and the inconspicuous cytological atypia of foamy gland carcinoma. Four cases had a Gleason score of 6. In the prostatectomies, the neoplasm was limited to the prostatic gland. The evolution has been favorable in all patients after 3 years of follow-up, on average. The cases reported herein demonstrate that PHA and foamy adenocarcinoma may be associated and occasionally show overlapping histological criteria. The PHA with foamy changes must be distinguished from conventional foamy adenocarcinoma and PHA because it can closely resemble hyperplastic glands mainly in needle prostatic biopsy.

Morphologic Updates in Prostate Pathology

In the past several years, modifications have been made to the original Gleason system with resultant therapeutic and prognostic implications. Several morphologic variants of prostatic adenocarcinoma have also been described. Prostate pathology has also evolved over the years with the discovery and utility of new immunohistochemical stains. The topics discussed in this update include the Gleason grading system, prognostic grade grouping, variants of prostatic adenocarcinoma, and the application of immunohistochemistry to prostate pathology.

Expression and significance of cortactin and HDAC6 in human prostatic foamy gland carcinoma

Cortactin, the cytoplasmic substrate of HDAC6, is known to play an actin cytoskeletal regulatory role which is implicated in the motility of cancer cells, and thus in cancer progression. Its activity is found to be regulated by HDAC6. However, the significance of cortactin and HDAC6 remains unclear in uncommon histologic variant human prostatic foamy gland carcinoma (PfCa). In this study, we aimed to identify the expression and potential role of cortactin and HDAC6 in PfCa. Therefore, 16 PfCa specimens containing 48 foci with distinctive lesions were collected to identify the status of cortactin and HDAC6 by immunohistochemistry. Their correlation between clinicopathological characteristics and prognostic values were further analysed. The effect of cortactin and HDAC6 on prostate cancer cell migration and invasion was then evaluated in IA8 cells. The results showed that expression of cortactin and HDAC6 was significantly higher in PfCa foci, compared to that of high-grade prostatic intraepithelial neoplasia (HGPIN) foci and benign foci (P < 0.05). Cortactin and HDAC6 were associated with poor prognosis of patients with PfCa (P < 0.05). Multivariable Cox regression analysis showed HDAC6 level was a significant prognostic factor for survival of patients with PfCa (β = 1.200, Wald value = 7.282, P = 0.007, 95% CI = 1.389-7.941, P < 0.01, β > 0). Both knocking down cortactin and inhibition of HDAC6 activity with tubacin reduced in vitro migration and invasion ability of IA8 cells substantially. Furthermore, HDAC6 has prognostic value for patients with PfCa. Dysregulation of cortactin and HDAC6 is implicated in the invasiveness and migration of prostate cancer cells.

Pseudohyperplastic prostate carcinoma: histologic patterns and differential diagnosis

The similarity between some carcinomas and many benign glandular proliferations has been mentioned in the literature for decades. The description of the main histologic features of pseudohyperplastic carcinoma has been very useful in avoiding errors of interpretation, particularly false-negative results. In recent years, we have found some histologic variants of this neoplasm that have not been mentioned previously. In order to classify the different histologic growth patterns and comment on their differential diagnosis, we reviewed the architectural and cytologic features of 34 cases of pseudohyperplastic adenocarcinoma in 2 radical prostatectomies, 4 transurethral resections, and 28 needle biopsies. Growth patterns most commonly observed included nodular, complex, and mixed (nodular and complex) patterns. Other less frequent histologic varieties included adenosis-like pattern, prostatic intraepithelial neoplasia-like pattern, pseudohyperplastic adenocarcinoma with xanthomatous features, and limited pseudohyperplastic adenocarcinoma. Frequent changes in neoplastic glands included papillary infoldings, large/cystic glands, and branching. Criteria associated with malignancy include nuclear enlargement (92%), apparent nucleoli (85%), pink amorphous secretions (78%), and transition to small acinar carcinoma (70%). However, in some biopsies, nuclear atypia was little apparent. Fifteen of the 34 cases were misdiagnosed as benign and 5 as other malignant neoplasms, and included the following diagnoses: hyperplastic nodules (11), prostatic adenosis (2), diffuse adenosis of the peripheral zone (1), benign cystic glands (1), and less frequently other malignant tumors including xanthomatous carcinoma (2), low-grade prostatic adenocarcinoma (2), and atrophic carcinoma (1). It is important to recognize the different growth patterns of this neoplasm in order to avoid an underdiagnosis of malignancy.

Foamy gland carcinoma in core needle biopsies of the prostate: clinicopathologic and immunohistochemical study of 56 cases

Foamy gland carcinoma is a subtype of acinar adenocarcinoma characterized by foamy appearance, large cytoplasm, pyknotic nuclei, inconspicuous nucleoli and infiltrative pattern. In this study, we investigated the histological features and the incidence of foamy gland carcinoma. We compared foamy gland carcinoma with acinar adenocarcinoma according to age, prostate-specific antigen value, Gleason score, peripheral nerve invasion and accompanying high-grade prostatic intraepithelial neoplasia. Besides, we investigated the diagnostic value of immunohistochemical markers in foamy gland carcinoma. A total of 863 TRUS-guided prostate needle core biopsies performed at our hospital pathology clinic between January 1, 2010, and December 31, 2011, were examined, 251 of these were diagnosed acinar type adenocarcinoma. Conventional acinar type adenocarcinoma was present in 195 (78%) cases, and foamy gland carcinoma, in 56 cases (22%). We found that 11 (19%) of the 56 foamy gland carcinoma cases were pure and 45 (81%) cases were mixed with conventional acinar type adenocarcinoma. Single-core localization was present in 7 of 14 pure foamy gland carcinomas, and the number of cases with a Gleason score of 7 and above was 21 (37%). No statistically significant difference was found between foamy gland carcinoma and conventional acinar type adenocarcinoma in terms of age, Gleason score, high-grade prostatic intraepithelial neoplasia, and prostate-specific antigen values. Peripheral nerve invasion was found to be statistically significantly more common in foamy gland carcinoma compared to acinar type adenocarcinoma (P<.05). The staining percentage of immunohistochemical markers in foamy gland carcinoma was 90.1% for p63, 90.6% for 34Beta12 and 90.6% for AMACR.

Pseudohyperplastic prostate adenocarcinoma with signet ring cells mimicking hyperplastic colonic polyp and associated high grade foamy gland carcinoma. A case report

Prostatic adenocarcinoma which closely mimics benign prostatic hyperplasia is adenocarcinoma with pseudohyperplastic pattern. The morphological similarities include large glands with papillary infoldings and branching. However the distinguishing features are crowded glands, nuclear enlargement, occasional to frequent nucleoli and abundant pink intraluminal secretions and crystals. There can be large glands with straight luminal borders. These tumors are not only difficult to diagnose but they are also difficult to grade as Gleason scoring system does not account for this histologic pattern. Some of these tumors have shown extraprostatic extension and it has been recommended that pseudohyperplastic adenocarcinoma should not be regarded as a low grade cancer. This is a case report of prostatic adenocarcinoma with pseudohyperplastic pattern and signet ring cells in the glandular epithelium mimicking colonic hyperplastic polyp. In addition there is an associated pattern of high grade foamy gland carcinoma and occasional signet ring cells in the stroma. This combination has not been described in previous studies.

Foamy gland carcinoma of the prostate in needle biopsy: incidence, Gleason grade, and comparative α-methylacyl-CoA racemase vs. ERG expression

Foamy gland carcinoma is a variant of prostatic acinar adenocarcinoma characterized by abundant, foamy cytoplasm, frequently showing small, pyknotic nuclei. The incidence and Gleason grade of foamy gland carcinoma in a large prostate needle biopsy series have not been established. Foamy gland carcinoma may be deceptively benign appearing and missed on needle biopsy. Immunohistochemical staining for basal cells and α-methylacyl-CoA racemase (AMACR) can support a diagnosis of foamy gland carcinoma, but the sensitivity of AMACR for foamy gland carcinoma has been reported to be lower than that for usual acinar carcinoma. The utility of ERG immunohistochemistry in the diagnosis of foamy gland carcinoma has not been explored. The aim of this study was to characterize the incidence and Gleason grade of foamy gland carcinoma in a large consecutive series of prostate needle biopsy cases. We also assessed ERG expression in foamy gland carcinoma, in comparison with AMACR expression, to determine whether ERG expression provides added diagnostic value beyond AMACR expression. We evaluated a consecutive series of 476 prostatic adenocarcinoma needle core biopsy cases for presence, linear extent, and Gleason grade of foamy gland carcinoma. A selected block from each case containing foamy gland carcinoma was evaluated for AMACR and ERG expression by immunohistochemistry. Of the 476 cases, 17% contained a foamy gland carcinoma component, with 2% of the cases showing pure foamy gland carcinoma. Two cases of pure foamy gland carcinoma had a total linear extent of <3 mm. The majority (80%) of cases had a Gleason score 3+3=score of 6. Sensitivity of AMACR for foamy gland carcinoma was 92%, and sensitivity of ERG was 42%. No AMACR-negative case was ERG positive. Low AMACR expression was detected in 24 of 72 cases (33%), and of these cases ERG was positive in 5 (21%). In summary, foamy gland carcinoma features are relatively common in prostate needle core biopsies, the foamy gland carcinoma is admixed with usual acinar carcinoma in the majority of cases, and is usually not of high Gleason grade, although 20% are Gleason score 7 or greater. ERG immunohistochemistry did not provide added value beyond AMACR expression in most cases, suggesting that it need not be initially utilized in addition to basal cell markers and AMACR when immunohistochemistry is needed to substantiate a diagnosis of foamy gland malignancy. This is an important consideration in this era of cost-consciousness in application of immunohistochemistry. Sensitivity of AMACR for foamy gland carcinoma was comparable to that seen in studies of usual acinar carcinoma and is an excellent marker for foamy gland carcinoma of the prostate. ERG immunohistochemistry could be considered in a second round of immunostaining of select difficult cases of foamy gland carcinoma with low AMACR expression.

Case report: Papillary mesothelioma of the peritoneum with foamy cell lining

A 34-year-old female, with a history of continued asbestos exposure, presented with a papillary peritoneal mesothelioma with a diffuse, prominent clear foamy cell change, with microvacuolation in its papillary lining, that expressed cytokeratins 7, 5/6 and calretinin as well as nuclear WT-1 and apical membrane staining for thrombomodulin, podoplanin D2-40 and HBME-1. In contrast, lining cells were CD68 negative. Foamy cell change has been reported in isolated cases as solid cords but not as a diffuse change in the mesothelial papillary lining. This phenomenon prompts differential diagnoses with abdominal and renal papillary clear cell tumours, which were discarded after a characteristic mesothelial immunophenotype was demonstrated.

VIRTUAL SLIDES

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/4679576081031834.

Variants and unusual patterns of prostate cancer: clinicopathologic and differential diagnostic considerations

Beyond the typical acinar morphology observed in the majority of prostatic adenocarcinomas, a spectrum of morphologic variants and prostate cancer subtypes exists. These unusual entities may be classified as: (1) cancer morphologies arising by divergent differentiation of prostatic ductal, acinar, or basal cells and associated with unique clinical features and/or therapeutic approaches, and (2) histologies occurring in the context of usual prostatic adenocarcinoma that may result in diagnostic misinterpretation or difficulties in Gleason grade assignment, especially in limited samples. This article details a number of variants, with emphasis on diagnostic criteria, differential diagnoses, and clinical significance.

False-negative prostate needle biopsies: frequency, histopathologic features, and follow-up

Little is known about the frequency, histopathologic characteristics, and clinical consequences of false-negative prostate biopsies, that is, biopsies classified as benign but containing adenocarcinoma or atypical suspicious glands [atypical small acinar proliferations (ASAP)]. Objective of this study was to evaluate false-negative prostate biopsy in a prostate cancer screening setting. Prostate biopsy sets of 196 participants of a screening trial, which had been reported as "benign" at initial diagnosis, followed by a diagnosis of adenocarcinoma in a subsequent screening round were reviewed by 2 urologic pathologists. Adenocarcinoma was identified in 19 biopsy cores corresponding to 16 (8.2%) patients and ASAP in 24 cores, corresponding to 19 patients (9.7%). All missed prostate cancers were Gleason score 6 (3+3). After correction for patient selection, the overall false-negative biopsy rate was estimated to be 2.4%; 1.1% for prostate cancer; and 1.3% for ASAP. Clinicopathologic features at the time of initial biopsy and of subsequent prostate cancer diagnosis did not differ between patients with a false-negative or true benign biopsy. Relatively low number of atypical glands (<10 glands), intense intermingling with preexistent glands or lack of architectural disorganization were the most prominent risk factors for a false-negative diagnosis. Another potential pitfall was the presence of prostate cancer variants, as 1 adenocarcinoma was of foamy gland type and 3 of pseudohyperplastic type. Routine examination of at least 1 level of prostate biopsy sets at high magnification and awareness of histologic prostate cancer variants might reduce the risk of missing or misinterpreting a relevant lesion at prostate biopsy evaluation.

An update of the Gleason grading system

PURPOSE

An update is provided of the Gleason grading system, which has evolved significantly since its initial description.

MATERIALS AND METHODS

A search was performed using the MEDLINE(R) database and referenced lists of relevant studies to obtain articles concerning changes to the Gleason grading system.

RESULTS

Since the introduction of the Gleason grading system more than 40 years ago many aspects of prostate cancer have changed, including prostate specific antigen testing, transrectal ultrasound guided prostate needle biopsy with greater sampling, immunohistochemistry for basal cells that changed the classification of prostate cancer and new prostate cancer variants. The system was updated at a 2005 consensus conference of international experts in urological pathology, under the auspices of the International Society of Urological Pathology. Gleason score 2-4 should rarely if ever be diagnosed on needle biopsy, certain patterns (ie poorly formed glands) originally considered Gleason pattern 3 are now considered Gleason pattern 4 and all cribriform cancer should be graded pattern 4. The grading of variants and subtypes of acinar adenocarcinoma of the prostate, including cancer with vacuoles, foamy gland carcinoma, ductal adenocarcinoma, pseudohyperplastic carcinoma and small cell carcinoma have also been modified. Other recent issues include reporting secondary patterns of lower and higher grades when present to a limited extent, and commenting on tertiary grade patterns which differ depending on whether the specimen is from needle biopsy or radical prostatectomy. Whereas there is little debate on the definition of tertiary pattern on needle biopsy, this issue is controversial in radical prostatectomy specimens. Although tertiary Gleason patterns are typically added to pathology reports, they are routinely omitted in practice since there is no simple way to incorporate them in predictive nomograms/tables, research studies and patient counseling. Thus, a modified radical prostatectomy Gleason scoring system was recently proposed to incorporate tertiary Gleason patterns in an intuitive fashion. For needle biopsy with different cores showing different grades, the current recommendation is to report the grades of each core separately, whereby the highest grade tumor is selected as the grade of the entire case to determine treatment, regardless of the percent involvement. After the 2005 consensus conference several studies confirmed the superiority of the modified Gleason system as well as its impact on urological practice.

CONCLUSIONS

It is remarkable that nearly 40 years after its inception the Gleason grading system remains one of the most powerful prognostic factors for prostate cancer. This system has remained timely because of gradual adaptations by urological pathologists to accommodate the changing practice of medicine.

Postchemotherapy histiocyte-rich pseudotumor involving the spleen

We report 2 cases of splenic postchemotherapy histiocyte-rich pseudotumor. Each patient had a history of diffuse large B-cell lymphoma, treated with multiagent chemotherapy. Computed tomography scans performed on both patients showed splenic masses. A positron emission tomography scan performed on 1 patient showed increased metabolic activity. The preoperative diagnosis in both patients was recurrent lymphoma, prompting splenectomy. The splenectomy specimens showed multiple, tan-white, firm nodules, up to 3.5 cm in diameter, that were histologically composed of central necrotic B cells (CD20+/CD3-), consistent with necrotic lymphoma, surrounded by numerous lipid-laden (xanthomatous) histiocytes. Clinical staging studies at the time of splenectomy showed no other sites of disease. We conclude that these histologic and immunophenotypic findings represent chemotherapy-induced tumor necrosis with a florid histiocytic reaction mimicking residual viable lymphoma. Others have used descriptive terminology or the term xanthomatous pseudotumor for these lesions that have been only rarely reported in the spleen previously.

Variants and Unusual Patterns of Prostate Cancer

Beyond the typical acinar morphology observed in most prostatic adenocarcinoma, a spectrum of morphologic variants and prostate cancer subtypes exists. These unusual entities may be further classified into (1) cancer morphologies arising by divergent differentiation of prostatic ductal, acinar, or basal cells and associated with unique clinical features or therapeutic approaches, and (2) histologies occurring in the context of usual prostatic adenocarcinoma that may result in diagnostic misinterpretation or difficulties in Gleason grade assignment, especially in limited samples. This article details several variants, with emphasis on diagnostic criteria, differential diagnoses, and clinical significance.

Benign Mimickers of Prostate Adenocarcinoma on Needle Biopsy and Transurethral Resection

Prostate needle biopsy currently is the gold standard method for the diagnosis, management, and prognosis of prostate cancer. Obtaining an accurate diagnosis is crucial for pursuing proper patient management. This article discusses histologic mimickers of prostate carcinoma highlighting microscopic features that are helpful to reach a correct diagnosis and emphasizing potential diagnostic pitfalls.

Xanthoma of the Prostate

Prostatic xanthoma may mimic high-grade prostatic adenocarcinoma or prostate cancer treated with hormone therapy. From 1995 to 2006, 40 cases of prostatic xanthoma were diagnosed at The Johns Hopkins Hospital. Thirty-four cases were received in consultation from outside institutions. Hematoxylin and eosin-stained or unstained slides were available in 27 cases (24 consultation cases; 3 in-house cases). Xanthoma was found on needle biopsy in 25 cases, with 2 cases noted on transurethral resection of prostate. Twenty-six cases contained only 1 focus of prostatic xanthoma with 1 case having 3 foci on the same core biopsy specimen. In 21 xanthomas, the lesions were small measuring <or=0.5 mm. Only 3 xanthomas were >1 mm with the largest one measuring 2.5 mm. Xanthoma cells had small uniform, benign-appearing nuclei, small inconspicuous nucleoli, and abundant vacuolated foamy cytoplasm. No mitoses were identified. Focal necrosis was identified in 1 case. Most xanthomas were arranged in circumscribed solid nodular pattern (17 cases). Ten xanthomas consisted of cords and individual cells infiltrating the prostatic stroma, further mimicking high-grade prostate carcinoma. Two xanthomas contained a mixed circumscribed nodular pattern and infiltrating pattern. Of cases with the lesion still present on slides for immunohistochemistry, CD68 was diffusely strongly positive in 18/19 (94.7%) and CAM5.2 was positive in none of the cases 0/14 (0%). One of 15 (6.7%), 2/17 (11.8%), and 1/12 (8.3%) cases were positive for prostate-specific antigen, prostate-specific acid phosphatase, and alpha-methylacyl-CoA racemase, respectively. Careful attention to morphology with adjunctive use of CD68 and CAM5.2 immunohistochemical stains are helpful in the diagnosis of prostatic xanthoma, especially in difficult cases with an infiltrative pattern.

Morphological features of TMPRSS2-ERG gene fusion prostate cancer

The TMPRSS2-ETS fusion prostate cancers comprise 50-70% of the prostate-specific antigen (PSA)-screened hospital-based prostate cancers examined to date, making it perhaps the most common genetic rearrangement in human cancer. The most common variant involves androgen-regulated TMPRSS2 and ERG, both located on chromosome 21. Emerging data from our group and others suggests that TMPRSS2-ERG fusion prostate cancer is associated with higher tumour stage and prostate cancer-specific death. The goal of this study was to determine if this common somatic alteration is associated with a morphological phenotype. We assessed 253 prostate cancer cases for TMPRSS2-ERG fusion status using an ERG break-apart FISH assay. Blinded to gene fusion status, two reviewers assessed each tumour for presence or absence of eight morphological features. Statistical analysis was performed to look for significant associations between morphological features and TMPRSS2-ERG fusion status. Five morphological features were associated with TMPRSS2-ERG fusion prostate cancer: blue-tinged mucin, cribriform growth pattern, macronucleoli, intraductal tumour spread, and signet-ring cell features, all with p-values < 0.05. Only 24% (n=30/125) of tumours without any of these features displayed the TMPRSS2-ERG fusion. By comparison, 55% (n=38/69) of cases with one feature (RR=3.88), 86% (n=38/44) of cases with two features (RR=20.06), and 93% (n=14/15) of cases with three or more features (RR=44.33) were fusion positive (p<0.001). To our knowledge, this is the first study that demonstrates a significant link between a molecular alteration in prostate cancer and distinct phenotypic features. The strength of these findings is similar to microsatellite unstable colon cancer and breast cancer involving BRCA1 and BRCA2 mutations. The biological effect of TMPRSS2-ERG overexpression may drive pathways that favour these common morphological features that pathologists observe daily. These features may also be helpful in diagnosing TMPRSS2-ERG fusion prostate cancer, which may have both prognostic and therapeutic implications.

Diagnosis of adenocarcinoma in prostate needle biopsy tissue

Prostate cancer is a major public health problem throughout the developed world. For patients with clinically localised prostate cancer, the diagnosis is typically established by histopathological examination of prostate needle biopsy samples. Major and minor criteria are used to establish the diagnosis, based on the microscopic appearance of slides stained using haematoxylin and eosin. Major criteria include an infiltrative glandular growth pattern, an absence of basal cells and nuclear atypia in the form of nucleomegaly and nucleolomegaly. In difficult cases, basal cell absence may be confirmed by immunohistochemical stains for high-molecular-weight cytokeratins (marked with antibody 34betaE12) or p63, which are basal cell markers. Minor criteria include intraluminal wispy blue mucin, pink amorphous secretions, mitotic figures, intraluminal crystalloids, adjacent high-grade prostatic intraepithelial neoplasia, amphophilic cytoplasm and nuclear hyperchromasia. Another useful diagnostic marker detectable by immunohistochemistry is alpha-methylacyl coenzyme A racemase (AMACR), an enzyme selectively expressed in neoplastic glandular epithelium. Cocktails of antibodies directed against basal cell markers and AMACR are particularly useful in evaluating small foci of atypical glands, and in substantiating a diagnosis of a minimal adenocarcinoma. Reporting of adenocarcinoma in needle biopsy specimens should always include the Gleason grade and measures of tumour extent in the needle core tissue. Measures of tumour extent are (1) number of cores positive for cancer in the number of cores examined, (2) percentage of needle core tissue affected by carcinoma and (3) linear millimetres of carcinoma present.

Stratified epithelium in prostatic adenocarcinoma: a mimic of high-grade prostatic intraepithelial neoplasia

Typically glands of prostatic adenocarcinoma have a single cell lining, although stratification can be seen in invasive carcinomas with a cribriform architecture, including ductal carcinoma. The presence and diagnostic significance of stratified cells within non-cribriform carcinomatous prostatic glands has not been well addressed. The histomorphological features and immunohistochemical profile of cases of non-cribriform prostatic adenocarcinoma with stratified malignant glandular epithelium were analyzed. These cases were identified from needle biopsy cases from the consultation files of one of the authors and from a review of 150 consecutive in-house needle biopsy cases of prostatic adenocarcinoma. Immunohistochemistry was performed utilizing antibodies reactive against high molecular weight cytokeratin (34betaE12), p63 and alpha-methylacyl-coenzyme-A racemase (AMACR). A total of 8 cases were identified, including 2 from the 150 consecutive in-house cases (1.3%). In 4 cases, the focus with glands having stratified epithelium was the sole carcinomatous component in the biopsy, while such a component represented 5-30% of the invasive carcinoma seen elsewhere in the remaining cases. The main attribute in all these foci was the presence of glandular profiles lined by several layers of epithelial cells with cytological and architectural features resembling flat or tufted high-grade prostatic intraepithelial neoplasia, but lacking basal cells as confirmed by negative 34betaE12 and/or p63 immunostains in all cases. The AMACR staining profile of the stratified foci was variable, with 4 foci showing positivity, and 3 foci being negative, including two cases that displayed AMACR positivity in adjacent non-stratified prostatic adenocarcinoma. Prostatic adenocarcinoma with stratified malignant glandular epithelium can be identified in prostate needle biopsy samples harboring non-cribriform prostatic adenocarcinoma and resembles glands with high-grade prostatic intraepithelial neoplasia. These 'PIN-like' carcinomas can present in pure form. Recognition of this pattern of prostatic adenocarcinoma is necessary to correctly diagnose such cases as invasive carcinoma.

Detection of prostate cancer by alpha-methylacyl CoA racemase (P504S) in needle biopsy specimens previously reported as negative for malignancy

AIMS

To investigate the possibility of detecting small focal prostatic cancer by alpha-methylacyl CoA racemase (AMACR)/P504S immunohistochemistry on needle biopsy specimens that were previously interpreted as negative for carcinoma on routine haematoxylin and eosin (H&E)-stained sections.

METHODS

Prostate needle biopsy specimens (n = 793) previously interpreted as benign prostatic tissue by conventional morphology from 239 patients with prostatic cancer diagnosed in other biopsy cores taken at the same biopsy session were stained with the P504S monoclonal antibody. If a biopsy specimen stained positively, two pathologists independently reviewed the original corresponding H&E-stained sections to establish the malignant diagnosis.

RESULTS

Eighty-four of the 793 biopsy specimens showed AMACR immunoreactivity; nine of these (9/793, 1.1%) contained previously unrecognized small focal prostatic carcinoma (Gleason 6, N = 8; Gleason 8, N = 1). Six of nine (67%) carcinomas showed foamy/pseudohyperplastic (N = 3) or atrophic (N = 3) features. Additionally, five biopsy specimens (5/793, 0.6%) with positive AMACR staining that did not meet the criteria for prostatic cancer on the original H&E slides were considered to be atypia.

CONCLUSIONS

In this study, we found a 1.1% false-negative rate for carcinoma on routine H&E-stained sections. AMACR immunohistochemical staining has shown the ability to improve detection of small focal prostatic carcinoma that could be missed by conventional histological examination.

Diagnostic utility of immunohistochemistry in morphologically difficult prostate cancer: review of current literature

Varma M & Jasani B (2005) Histopathology47, 1-16 Diagnostic utility of immunohistochemistry in morphologically difficult prostate cancer: review of current literatureImmunohistochemistry is widely used to distinguish prostate cancer from benign mimics and to establish the prostatic origin of poorly differentiated carcinoma. We critically review the recent advances in prostate cancer immunohistochemistry, including the introduction of newer basal cell markers such as p63 and the discovery of the overexpression of alpha-methylacyl coenzyme A racemase (AMACR) in prostate cancer. The description of newer urothelial markers to aid the distinction of prostate cancer from urothelial carcinoma is also presented together with refinements in the quality control of PSA and PSAP immunostaining. Although AMACR is a useful immunohistochemical marker for prostate cancer, it has significant limitations. These limitations are discussed and the need for interpreting AMACR immunoreactivity in the appropriate morphological context and in conjunction with basal call markers is emphasized. We also describe the utility of an immunohistochemical panel composed of PSA, PSAP and high molecular weight cytokeratin for distinguishing poorly differentiated prostate cancer from high-grade urothelial carcinoma. A morphological differential diagnosis based selection of immunohistochemical markers is highlighted as a novel approach in the diagnosis of prostate cancer in routine surgical pathology practice.

Immunohistochemistry in diagnostic surgical pathology of the prostate

Immunohistochemistry (IHC) can play an important role in diagnostic surgical pathology of the prostate. Basal cell markers, such as the 34betaE12 antibody and antibodies directed against cytokeratin 5 and 6 or p63, are very useful for demonstration of basal cells as their presence argues against a diagnosis of invasive prostatic carcinoma (PC). However, several benign mimickers of PC, including atrophy, atypical adenomatous hyperplasia (AAH), nephrogenic adenoma, and mesonephric hyperplasia, can stain negatively with these markers, and thus, a negative basal cell marker immunostain alone does not exclude a diagnosis of benignancy. Although there are examples in the literature of high grade PC that stain focally with some of the basal cell markers, these cases are usually readily diagnosed based on H&E appearances and are unlikely to be confused with these benign mimickers. Alpha-methylacyl-coenzyme-A racemase (AMACR) is a sensitive marker of PC (except for a few uncommon variants: atrophic, foamy gland, and pseudohyperplastic variants), and its detection by immunohistochemical staining in atypical prostatic lesions can be very useful in confirming an impression of adenocarcinoma. AMACR expression can also be identified in high grade prostatic intraepithelial neoplasia (PIN), prostatic atrophy, AAH, and benign prostatic glands, and accordingly, a diagnosis of PC should not be based solely on a positive AMACR immunostain, especially when the luminal staining is weak and/or noncircumferential. The use of AMACR/basal cell antibody cocktails has been found to greatly facilitate the distinction between PC and its benign mimickers, especially when only limited tissue is available for staining. Prostate specific antigen (PSA) and prostate specific acid phosphatase (PSAP) are both quite sensitive and fairly specific markers of PC (there are a few nonprostatic tumors that can express one or both), and are both very helpful in establishing or confirming the diagnosis of PC when the differential diagnosis includes other tumors that can involve the prostate such as urinary bladder urothelial carcinoma. 34betaE12, p63, thrombomodulin, and uroplakin III are additional urothelial associated markers useful in this differential diagnosis. CDX2 and villin are useful markers to diagnostically separate colonic adenocarcinoma from PC. AMACR positivity and negative basal cell marker reactions are useful to confirm the presence of residual PC after hormonal or radiation therapy. Pan-cytokeratin, PSA, and PSAP can also highlight subtle infiltrates of PC with hormonal or radiation therapy effect. PSA and PSAP immunohistochemical stains are valuable in confirming metastatic carcinoma as being of prostatic origin and should always be utilized in the diagnostic evaluation of metastatic adenocarcinoma of unknown primary origin in males.