Intraductal carcinoma of the prostate: interobserver reproducibility survey of 39 urologic pathologists

Clinical Management of Intraductal Carcinoma of the Prostate

Intraductal carcinoma of the prostate (IDC-P) has emerged as a distinct entity with significant clinical implications in prostate cancer (PCa) management. Despite historically being considered an extension of invasive PCa, IDC-P shows unique biological characteristics that challenge traditional diagnostic and therapeutic settings. This review explores the clinical management of IDC-P. While the diagnosis of IDC-P relies on specific morphological criteria, its detection remains challenging due to inter-observer variability. Emerging evidence underscores the association of IDC-P with aggressive disease and poor clinical outcomes across various PCa stages. However, standardized management guidelines for IDC-P are lacking. Recent studies suggest considering adjuvant and neoadjuvant therapies in specific patient cohorts to improve outcomes and tailor treatment strategies based on the IDC-P status. However, the current level of evidence regarding this is low. Moving forward, a deeper understanding of the pathogenesis of IDC-P and its interaction with conventional PCa subtypes is crucial for refining risk stratification and therapeutic interventions.

Cribriform Patterned Lesions in the Prostate Gland with Emphasis on Differential Diagnosis and Clinical Significance

Simple Summary

A cribriform structure is defined as a continuous proliferation of cells with intermingled lumina. Various entities may have a cribriform morphology within the prostate gland, ranging from normal, to benign, to borderline and even to malignant lesions. This review summarizes the morphologic features of entities that have a cribriform morphology within the prostate gland, with an emphasis on their differential diagnosis, molecular profile and clinical significance. The basic aim is to assist the pathologist with challenging and controversial cases and inform the clinician on the clinical implications of cribriform morphology.

Abstract

Cribriform glandular formations are characterized by a continuous proliferation of cells with intermingled lumina and can constitute a major or minor part of physiologic (normal central zone glands), benign (clear cell cribriform hyperplasia and basal cell hyperplasia), premalignant (high-grade prostatic intraepithelial neoplasia), borderline (atypical intraductal cribriform proliferation) or clearly malignant (intraductal, acinar, ductal and basal cell carcinoma) lesions. Each displays a different clinical course and variability in clinical management and prognosis. The aim of this review is to summarize the current knowledge regarding the morphological features, differential diagnosis, molecular profile and clinical significance of the cribriform-patterned entities of the prostate gland. Areas of controversy regarding their management, i.e., the grading of Intaductal Carcinoma, will also be discussed. Understanding the distinct nature of each cribriform lesion leads to the correct diagnosis and ensures accuracy in clinical decision-making, prognosis prediction and personalized risk stratification of patients.

Hidden clues in prostate cancer - Lessons learned from clinical and pre-clinical approaches on diagnosis and risk stratification

The heterogeneity of prostate cancer is evident at clinical, morphological and molecular levels. To aid clinical decision making, a three-tiered system for risk stratification is used to designate low-, intermediate-, and high-risk of disease progression. Intermediate-risk prostate cancers are the most frequently diagnosed, and even with common diagnostic features, can exhibit vastly different clinical progression. Thus, improved risk stratification methods are needed to better predict patient outcomes. Here, we provide an overview of the improvements in diagnosis/prognosis arising from advances in pathology reporting of prostate cancer, which can improve risk stratification, especially for patients with intermediate-risk disease. This review discusses updates to pathology reporting of morphological growth patterns, and proposes the utility of integrating prognostic biomarkers or innovative imaging techniques to enhance clinical decision-making. To complement clinical studies, experimental approaches using patient-derived tumors have highlighted important cellular and morphological features associated with aggressive disease that may impact treatment response. The intersection of urology, pathology and scientific disciplines is required to work towards a common goal of understanding disease pathogenesis, improving the stratification of patients with intermediate-risk disease and subsequently defining optimal treatment strategies using precision-based approaches.

Identification of Morphologic Criteria Associated with Biochemical Recurrence in Intraductal Carcinoma of the Prostate

Intraductal carcinoma of the prostate (IDC-P) is an aggressive subtype of prostate cancer strongly associated with an increased risk of biochemical recurrence (BCR). However, approximately 40% of men with IDC-P remain BCR-free five years after radical prostatectomy. In this retrospective multicenter study, we aimed to identify histologic criteria associated with BCR for IDC-P lesions. A total of 108 first-line radical prostatectomy specimens were reviewed. In our test cohort (n = 39), presence of larger duct size (>573 µm in diameter), cells with irregular nuclear contours (CINC) (≥5 CINC in two distinct high-power fields), high mitotic score (>1.81 mitoses/mm2), blood vessels, and comedonecrosis were associated with early BCR (<18 months) (p < 0.05). In our validation cohort (n = 69), the presence of CINC or blood vessels was independently associated with an increased risk of BCR (hazard ratio [HR] 2.32, 95% confidence interval [CI] 1.09-4.96, p = 0.029). When combining the criteria, the presence of any CINC, blood vessels, high mitotic score, or comedonecrosis showed a stronger association with BCR (HR 2.74, 95% CI 1.21-6.19, p = 0.015). Our results suggest that IDC-P can be classified as low versus high-risk of BCR. The defined morphologic criteria can be easily assessed and should be integrated for clinical application following validation in larger cohorts.

PTEN and DNA Ploidy Status by Machine Learning in Prostate Cancer

Simple Summary

Molecular tissue-based prognostic biomarkers are anticipated to complement the current risk stratification systems in prostate cancer, but their manual assessment is subjective and time-consuming. Objective assessment of such biomarkers by machine learning-based methods could advance their adoption in a clinical workflow. PTEN and DNA ploidy status are well-studied biomarkers, which can provide clinically relevant information in prostate cancer at a low cost. Using a cohort of 253 patients who received radical prostatectomy, we developed a novel, fully-automated PTEN scoring in immunohistochemically-stained tissue slides, which could be used to assess PTEN status in a reliable and reproducible manner. In an independent validation cohort of 259 patients, automatically assessed PTEN status was significantly associated with time to biochemical recurrence after radical prostatectomy, and the combination of PTEN and DNA ploidy status further improved risk stratification. These results demonstrate the utility of machine learning in biomarker assessment.

Abstract

Machine learning (ML) is expected to improve biomarker assessment. Using convolution neural networks, we developed a fully-automated method for assessing PTEN protein status in immunohistochemically-stained slides using a radical prostatectomy (RP) cohort (n = 253). It was validated according to a predefined protocol in an independent RP cohort (n = 259), alone and by measuring its prognostic value in combination with DNA ploidy status determined by ML-based image cytometry. In the primary analysis, automatically assessed dichotomized PTEN status was associated with time to biochemical recurrence (TTBCR) (hazard ratio (HR) = 3.32, 95% CI 2.05 to 5.38). Patients with both non-diploid tumors and PTEN-low had an HR of 4.63 (95% CI 2.50 to 8.57), while patients with one of these characteristics had an HR of 1.94 (95% CI 1.15 to 3.30), compared to patients with diploid tumors and PTEN-high, in univariable analysis of TTBCR in the validation cohort. Automatic PTEN scoring was strongly predictive of the PTEN status assessed by human experts (area under the curve 0.987 (95% CI 0.968 to 0.994)). This suggests that PTEN status can be accurately assessed using ML, and that the combined marker of automatically assessed PTEN and DNA ploidy status may provide an objective supplement to the existing risk stratification factors in prostate cancer.

Knowing what's growing: Why ductal and intraductal prostate cancer matter

Prostate cancer is a common malignancy, but only some tumors are lethal. Accurately identifying these tumors will improve clinical practice and instruct research. Aggressive cancers often have distinctive pathologies, including intraductal carcinoma of the prostate (IDC-P) and ductal adenocarcinoma. Here, we review the importance of these pathologies because they are often overlooked, especially in genomics and preclinical testing. Pathology, genomics, and patient-derived models show that IDC-P and ductal adenocarcinoma accompany multiple markers of poor prognosis. Consequently, "knowing what is growing" will help translate preclinical research to pinpoint and treat high-risk prostate cancer in the clinic.

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.

Interchangeability of light and virtual microscopy for histopathological evaluation of prostate cancer

Virtual microscopy (VM) holds promise to reduce subjectivity as well as intra- and inter-observer variability for the histopathological evaluation of prostate cancer. We evaluated (i) the repeatability (intra-observer agreement) and reproducibility (inter-observer agreement) of the 2014 Gleason grading system and other selected features using standard light microscopy (LM) and an internally developed VM system, and (ii) the interchangeability of LM and VM. Two uro-pathologists reviewed 413 cores from 60 Swedish men diagnosed with non-metastatic prostate cancer 1998–2014. Reviewer 1 performed two reviews using both LM and VM. Reviewer 2 performed one review using both methods. The intra- and inter-observer agreement within and between LM and VM were assessed using Cohen’s kappa and Bland and Altman’s limits of agreement. We found good repeatability and reproducibility for both LM and VM, as well as interchangeability between LM and VM, for primary and secondary Gleason pattern, Gleason Grade Groups, poorly formed glands, cribriform pattern and comedonecrosis but not for the percentage of Gleason pattern 4. Our findings confirm the non-inferiority of VM compared to LM. The repeatability and reproducibility of percentage of Gleason pattern 4 was poor regardless of method used warranting further investigation and improvement before it is used in clinical practice.

Intraductal Carcinoma of the Prostate: Pathogenesis and Molecular Perspectives

Intraductal carcinoma of the prostate (IDC-P), a clinicopathological entity characterized by malignant prostatic epithelial cells growing within ducts and/or acini, has a distinct architectural pattern, cytological features, and biological behavior. Whereas most IDC-P tumors could be derived from adjacent high-grade invasive cancer via retrograde spreading of cancer cells along benign ducts and acini, a small subset of IDC-P may arise from the transformation and intraductal proliferation of precancerous cells induced by various oncogenic events. These isolated IDC-P tumors possess a distinct mutational profile and may function as a carcinoma in situ lesion with de novo intraductal outgrowth of malignant cells. Further molecular characterization of these two types of IDC-P and better understanding of the mechanisms underlying IDC-P formation and progression could be translated into valuable biomarkers for differential diagnosis and actionable targets for therapeutic interventions. PATIENT SUMMARY: Intraductal carcinoma of the prostate is an aggressive type of prostate cancer associated with high risk for local recurrence and distant metastasis. In this review, we discussed pathogenesis, biomarkers, differential diagnoses, and therapeutic strategies for this tumor.

Head to head: should the intraductal component of invasive prostate cancer be graded?

The reporting of intraductal carcinoma of the prostate (IDCP) is controversial, with conflicting recommendations having recently been published by the International Society of Urological Pathology (ISUP) and the Genitourinary Pathology Society (GUPS). Both recommend that isolated (pure) IDCP should not be graded. However, the ISUP recommends incorporating the IDCP component of invasive prostate cancer in the Gleason score, whereas the GUPS recommends reporting IDCP as a comment, independently of the Gleason score. The arguments for and against incorporating the IDCP component of invasive prostate cancer in the Gleason score are discussed in detail.

Inter-observer variability of cribriform architecture and percent Gleason pattern 4 in prostate cancer: relation to clinical outcome

The Grade group is an important parameter for clinical decision-making in prostate cancer. Recently, percent Gleason pattern 4 and presence of invasive cribriform and/or intraductal carcinoma (CR/IDC) have been recognized for their independent predictive value for prostate cancer outcome. There is sparse data on the inter-observer agreement for these pathologic features in practice. Our objectives were to investigate inter-observer variability of percent Gleason pattern and CR/IDC and to relate individual tumour scores to clinical outcome. Our cohort included 80 consecutive radical prostatectomies with a median follow-up 87.1 months (interquartile range 43.3-119.2), of which the slide with largest tumour volume was scored by six pathologists for Grade group (four tiers: 1, 2, 3 and 4/5), percent Gleason pattern 4 (four tiers: 0-25%, 26-50%, 51-75% and 76-100%) and presence of CR/IDC (two tiers: absent, present). The individual assignments were related to post-operative biochemical recurrence (20/80). Inter-observer agreement was substantial (Krippendorff's α 0.626) for assessment of Grade group and moderate for CR/IDC (α 0.507) and percent Gleason pattern 4 (α 0.551). For each individual pathologist, biochemical recurrence rates incremented by Grade group and presence of CR/IDC, although such relation was less clear for percent Gleason pattern 4. In conclusion, inter-observer agreement for CR/IDC and percent Gleason pattern 4 is lower than for Grade groups, indicating awareness of these features needs further improvement. Grade group and CR/IDC, but not percent Gleason pattern 4 was related to biochemical recurrence for each pathologist, indicating overall validity of individual grade assignments despite inter-observer variability.

The 2019 International Society of Urological Pathology (ISUP) Consensus Conference on Grading of Prostatic Carcinoma

Five years after the last prostatic carcinoma grading consensus conference of the International Society of Urological Pathology (ISUP), accrual of new data and modification of clinical practice require an update of current pathologic grading guidelines. This manuscript summarizes the proceedings of the ISUP consensus meeting for grading of prostatic carcinoma held in September 2019, in Nice, France. Topics brought to consensus included the following: (1) approaches to reporting of Gleason patterns 4 and 5 quantities, and minor/tertiary patterns, (2) an agreement to report the presence of invasive cribriform carcinoma, (3) an agreement to incorporate intraductal carcinoma into grading, and (4) individual versus aggregate grading of systematic and multiparametric magnetic resonance imaging-targeted biopsies. Finally, developments in the field of artificial intelligence in the grading of prostatic carcinoma and future research perspectives were discussed.

Identification of intraductal carcinoma of the prostate on tissue specimens using Raman micro-spectroscopy: A diagnostic accuracy case-control study with multicohort validation

BACKGROUND

Prostate cancer (PC) is the most frequently diagnosed cancer in North American men. Pathologists are in critical need of accurate biomarkers to characterize PC, particularly to confirm the presence of intraductal carcinoma of the prostate (IDC-P), an aggressive histopathological variant for which therapeutic options are now available. Our aim was to identify IDC-P with Raman micro-spectroscopy (RμS) and machine learning technology following a protocol suitable for routine clinical histopathology laboratories.

METHODS AND FINDINGS

We used RμS to differentiate IDC-P from PC, as well as PC and IDC-P from benign tissue on formalin-fixed paraffin-embedded first-line radical prostatectomy specimens (embedded in tissue microarrays [TMAs]) from 483 patients treated in 3 Canadian institutions between 1993 and 2013. The main measures were the presence or absence of IDC-P and of PC, regardless of the clinical outcomes. The median age at radical prostatectomy was 62 years. Most of the specimens from the first cohort (Centre hospitalier de l'Université de Montréal) were of Gleason score 3 + 3 = 6 (51%) while most of the specimens from the 2 other cohorts (University Health Network and Centre hospitalier universitaire de Québec-Université Laval) were of Gleason score 3 + 4 = 7 (51% and 52%, respectively). Most of the 483 patients were pT2 stage (44%-69%), and pT3a (22%-49%) was more frequent than pT3b (9%-12%). To investigate the prostate tissue of each patient, 2 consecutive sections of each TMA block were cut. The first section was transferred onto a glass slide to perform immunohistochemistry with H&E counterstaining for cell identification. The second section was placed on an aluminum slide, dewaxed, and then used to acquire an average of 7 Raman spectra per specimen (between 4 and 24 Raman spectra, 4 acquisitions/TMA core). Raman spectra of each cell type were then analyzed to retrieve tissue-specific molecular information and to generate classification models using machine learning technology. Models were trained and cross-validated using data from 1 institution. Accuracy, sensitivity, and specificity were 87% ± 5%, 86% ± 6%, and 89% ± 8%, respectively, to differentiate PC from benign tissue, and 95% ± 2%, 96% ± 4%, and 94% ± 2%, respectively, to differentiate IDC-P from PC. The trained models were then tested on Raman spectra from 2 independent institutions, reaching accuracies, sensitivities, and specificities of 84% and 86%, 84% and 87%, and 81% and 82%, respectively, to diagnose PC, and of 85% and 91%, 85% and 88%, and 86% and 93%, respectively, for the identification of IDC-P. IDC-P could further be differentiated from high-grade prostatic intraepithelial neoplasia (HGPIN), a pre-malignant intraductal proliferation that can be mistaken as IDC-P, with accuracies, sensitivities, and specificities > 95% in both training and testing cohorts. As we used stringent criteria to diagnose IDC-P, the main limitation of our study is the exclusion of borderline, difficult-to-classify lesions from our datasets.

CONCLUSIONS

In this study, we developed classification models for the analysis of RμS data to differentiate IDC-P, PC, and benign tissue, including HGPIN. RμS could be a next-generation histopathological technique used to reinforce the identification of high-risk PC patients and lead to more precise diagnosis of IDC-P.

Reporting Practices and Resource Utilization in the Era of Intraductal Carcinoma of the Prostate: A Survey of Genitourinary Subspecialists

Intraductal carcinoma of the prostate (IDC-P) has been recently recognized by the World Health Organization classification of prostatic tumors as a distinct entity, most often occurring concurrently with invasive prostatic adenocarcinoma (PCa). Whether documented admixed with PCa or in its rare pure form, numerous studies associate this entity with clinical aggressiveness. Despite increasing clinical experience and requirement of IDC-P documentation in protocols for synoptic reporting, the specifics of its potential contribution to assessment of grade group (GG) and cancer quantitation of PCa in both needle biopsies (NBx) and radical prostatectomy (RP) specimens remain unclear. Moreover, there are no standard guidelines for incorporating basal cell marker immunohistochemistry (IHC) in the diagnosis of IDC-P, either alone or as part of a cocktail with AMACR/racemase. An online survey containing 26 questions regarding diagnosis, reporting practices, and IHC resource utilization, focusing on IDC-P, was undertaken by 42 genitourinary subspecialists from 9 countries. The degree of agreement or disagreement regarding approaches to individual questions was classified as significant majority (>75%), majority (51% to 75%), minority (26% to 50%) and significant minority (≤25%). IDC-P with or without invasive cancer is considered a contraindication for active surveillance by the significant majority (95%) of respondents, although a majority (66%) also agreed that the clinical significance/behavior of IDC-P on NBx or RP with PCa required further study. The majority do not upgrade PCa based on comedonecrosis seen only in the intraductal component in NBx (62%) or RP (69%) specimens. Similarly, recognizable IDC-P with GG1 PCa was not a factor in upgrading in NBx (78%) or RP (71%) specimens. The majority (60%) of respondents include readily recognizable IDC-P in assessment of linear extent of PCa at NBx. A significant majority (78%) would use IHC to confirm or exclude intraductal carcinoma if other biopsies showed no PCa, while 60% would use it to confirm IDC-P with invasive PCa in NBx if it would change the overall GG assignment. Nearly half (48%, a minority) would use IHC to confirm IDC-P for accurate Gleason pattern 4 quantitation. A majority (57%) report the percentage of IDC-P when present, in RP specimens. When obvious Gleason pattern 4 or 5 PCa is present in RP or NBx, IHC is rarely to almost never used to confirm the presence of IDC-P by the significant majority (88% and 90%, respectively). Most genitourinary pathologists consider IDC-P to be an adverse prognostic feature independent of the PCa grade, although recommendations for standardization are needed to guide reporting of IDC-P vis a vis tumor quantitation and final GG assessment. The use of IHC varies widely and is performed for a multitude of indications, although it is used most frequently in scenarios where confirmation of IDC-P would impact the GG assigned. Further study and best practices recommendations are needed to provide guidance with regards to the most appropriate indications for IHC use in scenarios regarding IDC-P.

Isolated Intraductal Carcinoma of the Prostate in Prostatectomy Specimens: Report of 2 Cases and Review of the Literature

Intraductal carcinoma of the prostate (IDCp) is a distinct neoplastic entity, and although recognized for some time, it was included for the first time in the histologic classification of prostate cancer in the 2016 publication of World Health Organization. IDCp represents an intraductal or intra-acinar proliferation of malignant cells, with preservation of the basal cell layer. Even though IDCp is usually accompanied by a high-grade invasive component, low-grade invasive carcinoma can rarely be seen adjacent to the lesion. Even rarer is the incidence of isolated IDCp in needle biopsies, while a few such cases have been reported in prostatectomy specimens. We report 2 cases with isolated IDCp without any invasive component. A review of the literature is performed including the diagnostic challenges of IDCp and its morphologic mimics, immunohistochemical markers, molecular aspects, and prognostic implications. Even though it is not yet clear whether IDCp represents an intraductal spread of invasive cancer or a precursor of invasive carcinoma, the existence of isolated IDCp reinforces the idea that, at least in some of the cases, IDCp is a precancerous lesion. Further molecular studies need to be performed in order to clarify its pathogenesis.

Stratification of Atypical Intraepithelial Prostatic Lesions Based on Basal Cell and Architectural Patterns

OBJECTIVES

High-grade prostatic intraepithelial neoplasia (HPIN) and atypical cribriform lesion of the prostate are considered the precursors or associators of invasive prostate cancer (iPCa). Given loss of basal cells being the hallmark of iPCa, we hypothesized that a subset of these atypical intraepithelial lesions (AILs) with sparse basal cells can be classified as prostatic intraepithelial carcinoma (PIC) with frequent iPCa association and that different morphologic patterns of PIC are associated with specific Gleason (G) patterns and scores for iPCa.

METHODS

We stratified 153 foci of AILs from 110 patients based on the integrity of the basal cell layer and architectural patterns and their association with iPCa.

RESULTS

We demonstrated that AILs could be stratified into usual HPIN (intact basal cell layer and simple patterns) with low-risk of iPCa association and PIC (sparse basal cell layer) with high risk of iPCa association. Furthermore, PIC could be divided into low-grade (simple patterns and associated with G3 and G3/4 iPCa) and high-grade PIC (complex patterns and associated with G4 and G3/4/5 iPCa).

CONCLUSIONS

Such stratification is of great clinical significance and instrumental to clinical patient management. It not only increases the predictability of AILs for iPCa but also accommodates a clinical scenario for lesions with features of intraductal carcinoma when iPCa is not found, particularly in biopsies.

[Grading of prostate cancer. For a more precise prognosis]

The simplification of the Gleason grading system, together with the reclassification of some of its patterns, has improved correlation with the clinical reality of prostate cancer, whilst maintaining the basic principles established fifty years ago. The subsequent grouping of the patterns into five degrees has allowed a more rational unification and enhanced the physician/patient communication. However, a greater precision in the assessment of the prognosis for each patient is still necessary and, to this end, elements that allow greater discrimination are continually being sought. The purpose of this brief review is to discuss the value and possible future incorporation in international recommendations of the percentage of pattern 4, the quantification of the cribriform pattern, the detection of intraductal carcinoma, the regrouping of some 'scores' and the possible stratification of the grade group 1.

Intraductal carcinoma of the prostate: a critical re-appraisal

Intraductal carcinoma of the prostate gland (IDCP), which is now categorised as a distinct entity by WHO 2016, includes two biologically distinct diseases. IDCP associated with invasive carcinoma (IDCP-inv) generally represents a growth pattern of invasive prostatic adenocarcinoma while the rarely encountered pure IDCP is a precursor of prostate cancer. This review highlights issues that require further discussion and clarification. The diagnostic criterion “nuclear size at least 6 times normal” is ambiguous as “size” could refer to either nuclear area or diameter. If area, then this criterion could be re-defined as nuclear diameter at least three times normal as it is difficult to visually compare area of nuclei. It is also unclear whether IDCP could also include tumours with ductal morphology. There is no consensus whether pure IDCP in needle biopsies should be managed with re-biopsy or radical therapy. A pragmatic approach would be to recommend radical therapy only for extensive pure IDCP that is morphologically unequivocal for high-grade prostate cancer. Active surveillance is not appropriate when low-grade invasive cancer is associated with IDCP, as such patients usually have unsampled high-grade prostatic adenocarcinoma. It is generally recommended that IDCP component of IDCP-inv should be included in tumour extent but not grade. However, there are good arguments in favour of grading IDCP associated with invasive cancer. All historical as well as contemporary Gleason outcome data are based on morphology and would have included an associated IDCP component in the tumour grade. WHO 2016 recommends that IDCP should not be graded, but it is unclear whether this applies to both pure IDCP and IDCP-inv.

Large-Gland Proliferations of the Prostate

Large-gland proliferations of the prostate have gained considerable attention in the past decade. The differential diagnosis is quite broad but can be refined using histologic criteria and, sometimes, immunostains. Pathologists have come to realize that cribriform and intraductal as well as ductal carcinomas are particularly aggressive patterns, and should name them in diagnostic reporting when present.

Comedonecrosis Revisited: Strong Association With Intraductal Carcinoma of the Prostate

From the advent of the Gleason grading system for prostate cancer, cancer displaying intraluminal necrotic cells and/or karyorrhexis within cribriform/solid architecture, a phenomenon termed "comedonecrosis," has been assigned pattern 5. Intraductal carcinoma (IDC-P) shows morphologic overlap with high-grade cribriform/solid adenocarcinoma architecturally and cytologically and may also show central necrosis, yet due to the presence of basal cells at the duct periphery is not currently assigned a grade in clinical practice. On the basis of observations from routine clinical cases, we hypothesized that comedonecrosis was more significantly associated with IDC-P than invasive disease. From a large series of mapped radical prostatectomy specimens (n=933), we identified 125 high-grade (≥Gleason score 4+3=7), high-volume tumors with available slides for review. All slides were examined for the presence of unequivocal comedonecrosis. Standard immunohistochemistry for basal cell markers was performed to detect basal cell labeling in these foci. In total, 19 of 125 (15%) cases showed some ducts with comedonecrosis-9 cases with 1 focus and 10 cases with ≥2 foci; in all, a total of 73 foci of true comedonecrosis were evaluated. Immunohistochemical stains revealed labeling for basal cell markers in a basal cell distribution for at least some comedonecrosis foci in 18 of 19 (95%) cases, 12 with IDC-P exclusively and 6 with a mix of IDC-P and invasive carcinoma comedonecrosis foci. These results suggest that comedonecrosis is strongly associated with IDC-P and hence, the routine assignment of pattern 5 to carcinoma exhibiting comedonecrosis should be reconsidered.

The New Realization About Cribriform Prostate Cancer

Data from the past 6 years have shown that the presence of any amount of cribriform (or more comprehensively, large acinar cribriform to papillary) pattern of invasive prostate cancer is associated with adverse pathologic features and leads to uniquely adverse outcomes. Sixteen papers and numerous abstracts have reached these conclusions concordantly. Not only does this justify removal of all cribriform cancer from Gleason grade 3, it shows that cribriform cancer has pathologic, outcome, and molecular features distinct from noncribriform Gleason grade 4. Suggestions for accommodating the presence of cribriform cancer into the 2014 Grade Group scheme are proposed.

Differential Diagnosis of Intraductal Lesions of the Prostate

The category of intraductal lesions of the prostate includes a range of primary prostatic and nonprostatic processes with wide variation in prognosis and recommended follow-up. Studies have shown that pathologists are uncomfortable with the diagnosis of these lesions and that the diagnostic reproducibility is low in this category. Despite the diagnostic difficulty, their accurate and reproducible diagnosis is critical for patient management. This review aims to highlight the diagnostic criteria, prognosis, and treatment implications of common intraductal lesions of the prostate. It focuses on the recognition of intraductal carcinoma of the prostate (IDC-P) in prostate needle biopsies and how to distinguish it from its common mimickers, including high-grade prostatic intraepithelial neoplasia, invasive cribriform prostatic adenocarcinoma, urothelial carcinoma extending into prostatic ducts, and prostatic ductal adenocarcinoma. IDC-P is independently associated with higher risk disease, and its identification in a needle biopsy, even in the absence of invasive carcinoma, should compel definitive treatment. Conversely, high-grade prostatic intraepithelial neoplasia has a much better prognosis and in limited quantities does not even warrant a repeat biopsy. IDC-P must be distinguished from urothelial carcinoma involving prostatic ducts, as recommended treatment varies markedly. Ductal adenocarcinoma may confuse the pathologist and clinician by overlapping terminology, and morphology may also mimic IDC-P on occasion. The use of ancillary testing with immunohistochemistry and molecular markers has also been reviewed.

Distinct DNA methylation alterations are associated with cribriform architecture and intraductal carcinoma in Gleason pattern 4 prostate tumors

The aim of the present study was to explore DNA methylation aberrations in association with cribriform architecture and intraductal carcinoma (IDC) of the prostate, as there is robust evidence that these morphological features are associated with aggressive disease and have significant clinical implications. Herein, the associations of a panel of seven known prognostic DNA methylation biomarkers with cribriform and IDC features were examined in a series of 91 Gleason pattern (GP) 4 tumors derived from Gleason score 7 radical prostatectomies. Gene specific DNA methylation was compared between cribriform and/or IDC positive vs. negative cases, and in association with clinicopathological features, using Chi square and Mann-Whitney U tests. DNA methylation of the adenomatous polyposis coli, Ras association domain family member 1 and T-box 15 genes was significantly elevated in GP4 tumors with cribriform and/or IDC features compared with negative cases (P=0.045, P=0.007 and P=0.013, respectively). To the best of our knowledge, this provides the first evidence for an association between cribriform and/or IDC and methylation biomarkers, and warrants further investigation of additional DNA methylation events in association with various architectural patterns in prostate cancer.

Intraductal carcinoma of prostate (IDC-P): from obscure to significant

The concept of intraductal carcinoma of prostate (IDC-P) has evolved over the years and its clinicopathologic significance has come to be more clearly appreciated. In contrast to morphologically malignant intraductal lesions that represent earlier stages of the malignant process in other anatomic sites such as the breast, IDC-P has now been generally recognized as a prognostically unfavorable manifestation of later stage spreading of its invasive counterpart. We here briefly review the evolution of the IDC-P concept, the histological diagnostic criteria and differential diagnosis, the clinical significance, as well as recent molecular data of IDC-P.

[Intraductal carcinoma of the prostate]

For many tumor entities, especially in breast cancer, an intraductal carcinoma is generally perceived as a precursor lesion, which precedes the emergence of invasive carcinoma. Therefore, in addition to parameters of the invasive carcinoma, histological parameters of the intraductal component have always played an important role in therapy planning of breast cancer. This is different in prostate cancer and although the term "intraductal carcinoma" has long been propagated by some authors, its routine use remains rare and inconsistent. This is certainly not only due to the far simpler therapy options of prostate cancer, in which focal and organ-preserving therapies still play a subordinate role, but also due to substantial interobserver variation and our inconsistent perception of intraductal carcinomas. This article gives a brief overview of currently available literature on this topic and explains why intraductal carcinoma of the prostate deserves our attention. In contrast to breast cancer, intraductal carcinoma of the prostate usually represents a post-invasive lesion, in which an aggressive tumor exhibits spread into pre-existing ducts; however, in rare cases, intraductal carcinoma may represent a true precursor lesion.