Pseudohyperplastic prostatic adenocarcinoma

Histological patterns, subtypes and aspects of prostate cancer: different aspects, different outcomes

PURPOSE OF REVIEW

The most common prostatic cancers (PCa) are acinary adenocarcinomas. Histological subtypes have been variably defined. The purpose of this review is to discuss unusual histological patterns and subtypes of acinar adenocarcinoma, as well as other types of PCa and their prognostic and therapeutic relevance.

RECENT FINDINGS

The new term 'subtype' for morphologically defined tumor entities replaced the term 'variant' in the new 2022 classification of the WHO to allow for clear terminological distinction from genetic variants. The 2022 WHO classification mentions prostatic intraepithelial neoplasia (PIN)-like carcinoma, signet-cell-like adenocarcinoma, sarcomatoid carcinoma and pleomorphic-giant-cell adenocarcinoma of the prostate as true subtypes of acinary PCa. Other forms of acinary PCa are termed unusual histological patterns and include atrophic, foamy-cell, microcystic, pseudohyperplastic and mucinous patterns. Nonacinar forms of prostate cancer include other glandular PCa, the ductal adenocarcinoma and the treatment-associated neuroendocrine carcinoma, and nonglandular PCa, the adenosquamous carcinoma, the squamous cell carcinoma and the adenoid cystic (basal cell) carcinoma of the prostate.

SUMMARY

True subtypes of acinary PCa and other forms of glandular and nonglandular PCa show relevant differences in prognosis and treatment approach compared with classic acinary PCa. The relevance of unusual histological patterns mainly lies in their deceptive benign appearance and the need for pathologists to know about these entities for accurate and timely diagnosis.

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.

Prostatic adenocarcinoma with a peculiar morphology – a rare case of pseudohyperplastic variant with inverted polarity

Background

The inverted (hobnail) variant of high-grade prostatic intraepithelial neoplasia (HGPIN) has been reported in two previous series and one case of inverted polarity in invasive adenocarcinoma has been reported. We reported an additional case of invasive carcinoma with this peculiar morphology.

Case presentation

We reported an additional case of invasive carcinoma with this peculiar morphology. A prostatectomy specimen of a 64-year-old patient showed a GG2 adenocarcinoma with extensive intraprostatic perineural infiltration and extraprostatic extension. Half of the entire tumor showed a distinctive inverted morphology.

Conclusion

Although pseudohyperplastic adenocarcinoma is believed to be a low-grade tumor to be graded as Gleason pattern 3, awareness of this morphology is important to collect more information on its biologic behavior and clinical implication.

A case of bulky pseudohyperplastic prostatic adenocarcinoma

A 67-year-old male with a pelvic mass 13 × 7 cm in dimension was diagnosed with a pseudohyperplastic prostatic adenocarcinoma via mass biopsy. Androgen-deprivation therapy was remarkably effective, resulting in rapid tumor shrinkage.

Comparison of Immunohistochemistry Expression of CK7, HMWK and PSA in High-Grade Prostatic Adenocarcinoma and Bladder Transitional Cell Carcinoma

Background & Objective:

Prostate adenocarcinoma is the most common malignancy in males, and the urothelial bladder carcinoma is also prevalent. The histological characteristic of these two tumors is very similar in high-grade cases, and their differentiation is difficult. This study was performed to compare the immunohistochemistry panel of high-grade prostate adenocarcinomas and high-grade urothelial bladder carcinomas.

Methods:

In this cross-sectional study, 36 cases of prostate adenocarcinoma and 36 urothelial bladder carcinoma samples were collected from the pathology department of Shahid Beheshti Hospital in Hamedan. For each sample, expression of Cytokeratin 7, high-molecular-weight cytokeratin and Prostate-specific antigen markers was evaluated by immunohistochemistry. Comparison of expression of these markers in high-grade bladder tumors and prostate tumors was made by SPSS 25 using Chi-square test.

Results:

In this study, the Cytokeratin 7 positivity was seen in 88.9% of bladder cancer versus 27.8% of prostate cancer samples. High-molecular-weight cytokeratin positive immunoreactivity was noted in 55.6% of bladder cancer and 5.6% of prostate cancer samples. Prostate-specific antigen marker showed positive results in 94.4% of prostate cancer samples, but no positivity was evident in those of bladder cancer.

Conclusion:

A panel of immunohistochemical stains can be used to differentiate high-grade prostate adenocarcinoma from urothelial bladder carcinoma in those cases which are challenging to diagnose.

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.

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.

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.

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.

Minimal (Limited) Pseudohyperplastic Prostatic Adenocarcinoma in Needle Prostatic Biopsy

Background. Study of minimum adenocarcinoma has been done almost exclusively on conventional acinar adenocarcinoma. Pseudohyperplastic adenocarcinoma can be confused with benign lesions because of its well-differentiated appearance and has not been studied when the biopsy shows few malignant glands (limited carcinoma). Methods. We reviewed 94 pseudohyperplastic adenocarcinomas diagnosed in prostatic biopsies for a period of 12 years and selected those measuring less than 1 mm or involving less than 5% of the biopsied tissue. We also reviewed 200 consecutive consultations. Results. Four (4.2%) of the 94 cases were limited pseudohyperplastic adenocarcinomas, and 3 were from consultations. Three of them were mistaken for hyperplastic nodules, prostatic adenosis, or prostatic intraepithelial neoplasm. The number of glands varied between 6 and 50 (average 23). Three nodular histological patterns were identified—nodular, adenosis-like, and pseudohyperplastic carcinoma resembling prostatic intraepithelial neoplasia. The diagnosis of adenocarcinoma was not related to the number of neoplastic glands. Histological criteria that were useful included: crowded medium to large glands, papillary infoldings, branching glands, straight luminal borders, hyperchromatic nuclei, nucleomegaly, and apparent nucleoli. Areas of transition to conventional acinar adenocarcinoma were useful in recognizing four of these neoplasms, but were barely apparent in 2 of them. Hyperchromatic nuclei were found in all cases, whereas apparent nucleoli and nucleomegaly were only present in 4. Conclusions. The architectural and cytological criteria for limited acinar adenocarcinoma are only partially useful in interpreting minimum pseudohyperplastic adenocarcinomas. Knowledge of the criteria for malignancy in both neoplasms is important in order to avoid underdiagnosis of malignancy.

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.

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.

HOXB13 G84E-related familial prostate cancers: a clinical, histologic, and molecular survey

Recent genetic epidemiologic studies identified a germline mutation in the homeobox transcription factor, HOXB13 G84E, which is associated with markedly increased risk for prostate cancer, particularly early-onset hereditary prostate cancer. The histomorphologic and molecular features of cancers arising in such carriers have not been studied. Here, we reviewed prostatectomy specimens from 23 HOXB13 G84E mutation carriers, mapping the total cancer burden by anatomically distinct cancer focus and evaluating morphologic features. We also assessed basic molecular subtypes for all cancer foci (ERG/SPINK1 status) by dual immunohistochemistry staining on full sections. The cohort showed a median age of 58 years, a median serum PSA level of 5.7 ng/mL, and a median of 6 cancer foci (range, 1 to 14) per case. Of evaluable cases, dominant foci were Gleason score 6 in 23%, 3+4=7 in 41%, 4+3=7 in 23%, and ≥8 in 14%; biochemical recurrence was observed in 1 case over a median of 36 months follow-up. Histologic review found a high prevalence of cases showing cancers with a spectrum of features previously described with pseudohyperplastic carcinomas, with 45% of cases showing a dominant focus with such features. Molecular subtyping revealed a strikingly low prevalence of ERG cancer with increased prevalence of SPINK1 cancer (dominant focus ERG 17%, SPINK1 26%, ERG/SPINK1 52%, single ERG/SPINK1 focus 4%). One ERG/SPINK1 dominant focus showed aberrant p63 immunophenotype. In summary, HOXB13 G84E variant-related prostate cancers show frequent pseudohyperplastic-type features and markedly low prevalence of ERG cancers relative to unselected cases and, especially, to early-onset cohorts. These findings suggest that novel molecular pathways may drive disease in HOXB13 G84E carriers.

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.

Clinical implications of current developments in genitourinary pathology

CONTEXT

Several developments in genitourinary pathology are likely to change our understanding and management of some genitourinary cancers considerably.

OBJECTIVE

To review 5 stories in genitourinary pathology: (1) fusion in the ETS (E26) gene family in prostatic adenocarcinoma; (2) insulin-like growth factor II messenger RNA-binding protein 3 (IMP3), an important prognostic biomarker for kidney and bladder cancers; (3) translocation renal cell carcinoma; (4) UroVysion fluorescence in situ hybridization test in urine cytology for detection of bladder cancer; and (5) the use of triple immunostaining for diagnosis of prostate cancer.

DATA SOURCES

Literature review and authors' personal experiences.

CONCLUSIONS

Many scientific findings have contributed recently to the understanding of the natural pathogenesis and progression of genitourinary cancers. This translational research helps in diagnosing, predicting, and potentially, treating genitourinary cancers.

Preneoplasia in the prostate gland with emphasis on high grade prostatic intraepithelial neoplasia

There are a variety of morphological patterns and processes that have been implicated in the pathogenesis of prostate cancer. Prostatic intraepithelial neoplasia (PIN), inflammation with or without atrophy, and adenosis (atypical adenomatous hyperplasia) have all been given candidate status as precursor lesions of prostatic adenocarcinoma. Based on decades of research, high grade prostatic intraepithelial neoplasia (HPIN), a proliferative lesion of prostatic secretory cells, has emerged as the most likely morphological pre-invasive lesion involved in the evolution of many but not all prostatic adenocarcinomas. In this manuscript, we briefly discuss other proposed precursors of prostatic adenocarcinoma and then focus on the history, diagnostic criteria and morphology of HPIN. The incidence of HPIN and its relationship to prostate cancer is reviewed. The differential diagnosis of large glandular patterns in the prostate is discussed in depth. Finally, we summarise the recent clinicopathological studies evaluating the clinical significance of HPIN and discuss follow-up strategies in men diagnosed with HPIN.

[Non-neoplastic alterations of the prostate. Why should pathologists know them?]

Non-neoplastic changes in the prostatic gland include inflammatory, atrophic, hyperplastic and metaplastic reaction patterns of the glandular epithelium and the fibromuscular stroma. Furthermore, histoanatomical structures from outside the prostatic gland are sometimes included in biopsy material. Knowledge of the morphological appearance of benign, reactive lesions is important in order to differentiate them from malignancies. To this aim knowing the precise location of tissue sampling as well as ancillary immunohistochemical investigations are often useful or necessary.

The spectrum of morphology in non-neoplastic prostate including cancer mimics

The spectrum of morphology in non-neoplastic prostate includes lesions of prostatic epithelial origin, the most common being atrophy, including partial atrophy, adenosis (atypical adenomatous hyperplasia), basal cell hyperplasia and crowded benign glands, as well as those of non-prostatic origin, such as seminal vesicle epithelium. These lesions often mimic lower-grade prostatic adenocarcinoma whereas others, such as granulomatous prostatitis, for example, are in the differential diagnosis of adenocarcinoma, Gleason grades 4 or 5. Diagnostic awareness of the salient histomorphological and relevant immunohistochemical features of these prostatic pseudoneoplasms is critical to avoid rendering false positive diagnoses of malignancy.

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.

Pseudoneoplastic mimics of prostate and bladder carcinomas

CONTEXT

The differential diagnoses of prostatic carcinoma and bladder epithelial neoplasms include several histologic mimics that should be known to avoid misdiagnosis.

OBJECTIVE

To discuss pseudoneoplastic lesions of the prostate and bladder that could potentially be confused with prostatic carcinoma and bladder epithelial neoplasms, respectively, with specific focus on their distinguishing histopathologic features.

DATA SOURCES

Relevant published literature and authors' experience.

CONCLUSIONS

Pseudoneoplastic lesions in the prostate include those of prostatic epithelial origin, the most common being atrophy, adenosis (atypical adenomatous hyperplasia), basal cell hyperplasia, and crowded benign glands, as well as those of nonprostatic origin, such as seminal vesicle epithelium. Such lesions often mimic lower-grade prostatic adenocarcinoma, whereas others, such as clear cell cribriform hyperplasia and granulomatous prostatitis, for example, are in the differential diagnosis of Gleason adenocarcinoma, Gleason grade 4 or 5. Pseudoneoplastic lesions of the urinary bladder include lesions that could potentially be confused with urothelial carcinoma in situ, such as reactive urothelial atypia, and others, such as polypoid/papillary cystitis, where papillary urothelial neoplasms are the main differential diagnostic concern. Several lesions can mimic invasive urothelial carcinoma, including pseudocarcinomatous hyperplasia, von Brunn nests, and nephrogenic adenoma. Diagnostic awareness of the salient histomorphologic and relevant immunohistochemical features of these prostatic and urinary bladder pseudoneoplasms is critical to avoid rendering false-positive diagnoses of malignancy.

Evaluation of routine application of P504S, 34betaE12 and p63 immunostaining on 250 prostate needle biopsy specimens

BACKGROUND

We aimed to determine whether a standard P504S, 34betaE12 and p63 immunostaining of prostate core needle biopsy specimens can optimize diagnostic accuracy of conventional staining methods.

MATERIALS AND METHODS

The staining properties of all three antibodies were evaluated on 250 prostate biopsies formerly diagnosed as benign.

RESULTS

Lack of basal cell staining in more than three glands for 34betaE12 and p63 occurred in 41 (27.5%) and 9 (6%) respective cases from the General Hospital pool. Respective figures from the Uropathology department specimens were 18 (18%) for 34betaE12 and 8 (8%) for p63. With the aid of P504S positivity, a case of prostate cancer as well as another of atypical small acinar proliferation was discovered.

CONCLUSION

Despite its potential for important aid in accurate diagnosis, standard application of immunohistochemistry in prostate biopsy is not justified and should be reserved for equivocal cases where conventional pathology fails to be conclusive.

What is the pathologist saying? Interpretation of the prostate pathology report

Management of patients presenting with elevated serum prostate-specific antigen levels, or those with previously diagnosed prostate carcinoma, is very much dependent on the pathology report on needle biopsy or radical prostatectomy specimens obtained from these patients. In contrast to a diagnosis of benignity or high-grade prostatic intraepithelial neoplasia, a diagnosis of atypia on needle core biopsy is usually an indication for a repeat biopsy; however, it is important to understand that atypia and other related terms are not specific diagnoses. The pathology report on different prostate specimens with a diagnosis of carcinoma usually includes the Gleason grade and extent of carcinoma among other morphological prognostic and predictive factors. Understanding the significance of these morphological factors and how they are evaluated and incorporated into the pathology report, as well as newer developments in this field, can assist urologists in the interpretation of the pathological findings and ultimately lead to better clinical care.

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.

Do prostatic transition zone tumors have a distinct morphology?

Previous studies have proposed that the morphologic spectrum of prostatic glands of variable size with tall columnar cells displaying basally oriented nuclei and clear to pale pink cytoplasm (TZ-LOOK) is characteristic of the well to moderately differentiated component of transition zone (TZ) tumors. However, the specificity of these findings has not been well studied. In a recent report, we identified dominant peripheral zone (PZ) and TZ tumors situated anterior to the prostatic urethra. Currently, we evaluate the histopathologic features of 215 dominant tumors, including 63 TZ and 73 anterior PZ lesions and an additional cohort of 79 posterior PZ tumors, in radical prostatectomy specimens, to identify the prevalence of this morphology in tumors of different zonal origin. Each dominant tumor was assigned a TZ-LOOK extent score of 0 to 4, with 0 = no such morphology, 1 = 1% to 25%, 2 = 26% to 50%, 3 = 51% to 75%, and 4 = >75%. Overall, 121/215 (56%) tumors showed some degree of this histology, including 56 of 63 (89%) TZ tumors and 65 of 152 (43%) PZ tumors (P<0.0001). Thirty-seven of 215 (17%) lesions had scores of 3 to 4, with 31 (84%) of these being of TZ origin. However, only 31/63 (49%) TZ tumors had >50% TZ-LOOK. Among PZ tumors, 6/152 (4%) had predominant (>50%) TZ-LOOK morphology, yet 23/152 (15%) of all PZ tumors and 23/65 (35%) of PZ tumors displaying any degree of TZ-LOOK had scores of 2 to 3 (>25%; nonfocal). In tumors of both zones with predominant (scores 3 to 4; >50%) TZ-LOOK histology, darker glands of usual acinar adenocarcinoma was often seen at the periphery. Conversely, in tumors with nonpredominant TZ-LOOK (scores 1 to 2; 50% of this histology are very likely of TZ origin, but this scenario occurs in only half of TZ tumors. Importantly, the TZ-LOOK is nonfocal in up to 35% of PZ tumors exhibiting any degree of this morphology. Given this lack of specificity, caution should be exercised in assigning zone of origin based on this histologic appearance, especially in limited samples such as prostate needle biopsy.

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.

Current prostate biopsy interpretation: criteria for cancer, atypical small acinar proliferation, high-grade prostatic intraepithelial neoplasia, and use of immunostains

CONTEXT

The past decade has brought major changes in prostate biopsy sampling, interpretation, and reporting.

OBJECTIVE

To summarize current information on diagnostic decision making, Gleason grading, "atypical" diagnoses, and use of immunostaining.

DATA SOURCES

Pertinent literature from 1985 to 2005 is reviewed, emphasizing recent findings.

CONCLUSIONS

Diagnosis begins by evaluating a focus of atypical single-cell layer lined acini according to the 3 minimal diagnostic criteria for cancer: an infiltrative pattern, nuclear enlargement and hyperchromasia, and prominent nucleoli. The Gleason score and linear extent or percent of each core containing cancer should be reported. Atypical small acinar proliferation suspicious for malignancy designates foci that have either qualitative or quantitative limitations in atypia precluding a definite cancer diagnosis. It has about a 3% incidence as an isolated finding. Contemporary studies indicate a 39% predictive value for cancer on repeat biopsy. Isolated high-grade prostatic intraepithelial neoplasia has a 3% to 14% incidence and predicts cancer on repeat biopsy in 23% of cases. Immunostaining for a marker of benign prostate (cytoplasmic keratin 34betaE12 or nuclear p63) and a marker of cancer (alpha-methylacyl coA racemase, clone P504S) may or may not resolve atypical small acinar proliferation diagnoses. Performance of 34betaE12 and P504S immunostains resolved 76% of atypical small acinar proliferation diagnoses per consensus of 3 urologic pathologists studied; a technical limitation is preservation of the focus in question on the levels used for immunostaining.

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.

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.

Diagnosis and reporting of limited adenocarcinoma of the prostate on needle biopsy

The diagnosis of limited adenocarcinoma of the prostate is one of the more difficult challenges in surgical pathology. This paper highlights the methodological approach to diagnosing limited cancer, based on a constellation of features more commonly present in adenocarcinoma than benign glands. In assessing small foci of atypical glands on needle biopsy, one looks for differences between the benign glands and the atypical glands in terms of nuclear features, cytoplasmic features, and intraluminal contents. Only a few features, such as glomerulations, mucinous fibroplasia (collagenous micronodules), and perineural invasion are diagnostic in and of themselves for prostate cancer. Immunohistochemistry may be a useful adjunct in the diagnosis of limited adenocarcinoma of the prostate, although as with any immunohistochemical studies, there are problems with both sensitivity and specificity. Basal cell markers, such as high molecular weight cytokeratin and more recently, p63, highlight basal cells found in benign glands, yet are absent in adenocarcinoma of the prostate. However, not all benign glands label uniformly with basal cell markers. Certain mimickers of adenocarcinoma of the prostate are even less frequently labeled uniformly with these stains. Consequently, negative staining in a small focus of atypical glands for basal cell markers is not diagnostic of adenocarcinoma of the prostate. More recently, a marker has been identified that relatively selectively labels adenocarcinoma of the prostate. AMACR will label the cytoplasm of approximately 80% of limited adenocarcinoma of the prostate cases on needle biopsy. In positive cases, not all of the glands will be positive and those that are positive are often not intensely positive. Certain variants of adenocarcinoma of the prostate that are a little more difficult to recognize, such as foamy glands adenocarcinoma, pseudohyperplastic adenocarcinoma, and atrophic adenocarcinoma, are labeled with AMACR in only approximately 60-70% of cases. In addition to problems with sensitivity, AMACR is not entirely specific for adenocarcinoma, and will label almost all cases of high-grade prostatic intraepithelial neoplasia, some foci of adenosis, and even some entirely benign glands. Finally, this paper will briefly cover the significance of atypical or suspicious prostate needle biopsies, and how to report the key diagnostic and prognostic information on needle biopsy.

Gleason grading and prognostic factors in carcinoma of the prostate

Gleason grade of adenocarcinoma of the prostate is an established prognostic indicator that has stood the test of time. The Gleason grading method was devised in the 1960s and 1970s by Dr Donald F Gleason and members of the Veterans Administration Cooperative Urological Research Group. This grading system is based entirely on the histologic pattern of arrangement of carcinoma cells in H&E-stained sections. Five basic grade patterns are used to generate a histologic score, which can range from 2 to 10. These patterns are illustrated in a standard drawing that can be employed as a guide for recognition of the specific Gleason grades. Increasing Gleason grade is directly related to a number of histopathologic end points, including tumor size, margin status, and pathologic stage. Indeed, models have been developed that allow for pretreatment prediction of pathologic stage based upon needle biopsy Gleason grade, total serum prostate-specific antigen level, and clinical stage. Gleason grade has been linked to a number of clinical end points, including clinical stage, progression to metastatic disease, and survival. Gleason grade is often incorporated into nomograms used to predict response to a specific therapy, such as radiotherapy or surgery. Needle biopsy Gleason grade is routinely used to plan patient management and is also often one of the criteria for eligibility for clinical trials testing new therapies. Gleason grade should be routinely reported for adenocarcinoma of the prostate in all types of tissue samples. Experimental approaches that could be of importance in the future include determination of percentage of high-grade Gleason pattern 4 or 5, and utilization of markers discovered by gene expression profiling or by genetic testing for DNA abnormalities. Such markers would be of prognostic usefulness if they provided added value beyond the established indicators of Gleason grade, serum prostate-specific antigen, and stage. Currently, established prognostic factors for prostatic carcinoma recommended for routine reporting are TNM stage, surgical margin status, serum prostate-specific antigen, and Gleason grade.

Benign mimickers of prostatic adenocarcinoma

The diagnosis of prostatic adenocarcinoma, especially when present in small amounts, is often challenging. Before making a diagnosis of carcinoma, it is prudent for the pathologist to consider the various benign patterns and processes that can simulate prostatic adenocarcinoma. A useful method of classifying benign mimickers is in relationship to the major growth patterns depicted in the classical Gleason diagram. The four major patterns are small gland, large gland, fused gland and solid. Most mimickers fit within the small gland category and the most common ones giving rise to false-positive cancer diagnosis are atrophy, post-atrophic hyperplasia, atypical adenomatous hyperplasia and seminal vesicle-type tissue. A number of other histoanatomic structures such as Cowper's gland, verumontanum mucosal glands, mesonephric glands and paraganglionic tissue may be confused with adenocarcinoma. Additionally, metaplastic and hyperplastic processes within the prostate may be confused with adenocarcinoma. Furthermore, inflammatory processes including granulomatous prostatitis, xanthogranulomatous prostatitis and malakoplakia may simulate high-grade adenocarcinoma. Atypical adenomatous hyperplasia (adenosis), a putative precursor of transition zone adenocarcinoma, has overlapping features with low-grade adenocarcinoma and may cause problems in differential diagnosis, especially in the needle biopsy setting. The pathologist's awareness of the vast array of benign mimickers is important in the systematic approach to the diagnosis of prostatic adenocarcinoma. Knowledge of these patterns on routine microscopy coupled with the prudent use of immunohistochemistry will lead to a correct diagnosis and avert a false-positive cancer interpretation.