Diagnosis of Cowper's glands on prostate needle biopsy

Benign mimics of prostate cancer

The histopathological diagnosis of prostatic adenocarcinoma is challenged by the existence of numerous benign mimics. Most of these lesions have no clinical significance and many do not need to be reported. Their clinical relevance lies in the risk that they are misinterpreted as cancer. This review presents the histopathological features of benign mimics and discusses their distinction from cancer. The lesions that are most often misdiagnosed as cancer are atrophy and its variants, including simple atrophy, partial atrophy and post-atrophic hyperplasia. Benign proliferations are a group of lesions with crowded small glands with no or little nuclear atypia. The most problematic entity of this group is adenosis, which may have a more alarming architecture than some cancers. A diagnostic problem with atrophy and several of the benign proliferations is that the glands often have a discontinuous or absent basal cell layer. Hyperplastic and metaplastic lesions include basal cell hyperplasia. Basal cell hyperplasia may especially mimic prostate cancer with its small dark glands, variable nuclear atypia and a pseudoinfiltrative pattern, which may be present. The anatomical structure that most often causes diagnostic problems is the seminal vesicle. The mucosa of the seminal vesicle contains small acini, often with very pronounced nuclear atypia that may be misinterpreted as cancer. Pathologists need to be familiar with these mimics, as a false positive diagnosis of prostate cancer may lead to unnecessary radical treatment.

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.

[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.

Precursors of prostate cancer

High-grade prostatic intraepithelial neoplasia (PIN) is the only accepted precursor of prostatic adenocarcinoma, according to numerous studies of animal models and man; other proposed precursors include atrophy and malignancy-associated changes (with no morphologic changes). PIN is characterized by progressive abnormalities of phenotype and genotype that are intermediate between benign prostatic epithelium and cancer, indicating impairment of cell differentiation and regulatory control with advancing stages of prostatic carcinogenesis. The only method of detection of PIN is biopsy because it does not significantly elevate serum prostate-specific antigen concentration and cannot be detected by ultrasonography. The mean incidence of PIN in biopsies is 9% (range, 4%-16%), representing about 115,000 new cases of isolated PIN diagnosed each year in the United States. The clinical importance of PIN is its high predictive value as a marker for adenocarcinoma, and its identification warrants repeat biopsy for concurrent or subsequent carcinoma, especially when multifocal or observed in association with atypical small acinar proliferation (ASAP). Carcinoma develops in most patients with PIN within 10 years. Androgen deprivation therapy and radiation therapy decrease the prevalence and extent of PIN, suggesting that these forms of treatment may play a role in prevention of subsequent cancer. Multiple clinical trials to date of men with PIN have had modest success in delaying or preventing subsequent cancer.

Diagnostic utility of α-methylacyl CoA racemase (P504S) & HMWCK in morphologically difficult prostate cancer

Background

To evaluate the diagnostic utility of alpha-methylacyl CoA racemase (P504S) & HMWCK (34beta E12) in morphologically difficult prostate cancer.

Methods

A total of 1034 cases were reviewed and divided into benign (585) malignant (399) and suspicious (50). Immunohistochemistry with HMWCK and AMACR was done on the 50 suspicious cases along with controls.

Results

Forty nine suspicious cases were resolved by using both markers where as 1 case was resolved by further support with CD68. The original diagnosis was changed in 15 of 50 (30%) suspicious cases from benign to malignant, one case from benign to high grade PIN and in one case from malignant to benign. Change of diagnosis was seen in 17 of 50 (34%) suspicious cases with a significant p value of 0.002. The overall diagnosis was changed in 17 of 1034 cases (1.64%) of prostatic disease (p < 0.001).

Conclusions

A combination of HMWCK and AMACR is of great value in combating the morphologically suspicious cases and significantly increasing the diagnostic accuracy in prostate cancer. Although, in this study the sensitivity and specificity of HMWCK and AMACR were high, yet it should be used with caution, keeping in mind all their pitfalls and limitations.

Benign Mimickers of Prostate Adenocarcinoma on Needle Biopsy and Transurethral Resection

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

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

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

Immunohistochemistry in diagnostic surgical pathology of the prostate

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

High-grade prostatic intraepithelial neoplasia

High-grade prostatic intraepithelial neoplasia (PIN) is now accepted as the most likely preinvasive stage of adenocarcinoma, almost two decades after its first formal description. PIN has a high predictive value as a marker for adenocarcinoma, and its identification warrants repeat biopsy for concurrent or subsequent invasive carcinoma. The only method of detection is biopsy; PIN does not significantly elevate serum prostate-specific antigen (PSA) concentration or its derivatives and cannot be detected by current imaging techniques, including ultrasound. Most patients with PIN will develop carcinoma within 10 years. PIN is associated with progressive abnormalities of phenotype and genotype, which are similar to cancer rather than normal prostatic epithelium, indicating impairment of cell differentiation with advancing stages of prostatic carcinogenesis. Androgen deprivation therapy decreases the prevalence and extent of PIN, suggesting that this form of treatment may play a role in chemoprevention.

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.

Prostatic foamy gland carcinoma with aggressive behavior: clinicopathologic, immunohistochemical, and ultrastructural analysis

Foamy gland carcinoma is a recently described histologic variant of prostatic adenocarcinoma characterized by abundant foamy cytoplasm and minimal cytologic atypia. The biologic behavior and biochemical nature of the foamy adenocarcinoma cells are unknown. Six cases of prostatic adenocarcinoma with marked foamy appearance were identified from radical prostatectomies. Clinicopathologic, histochemical, immunohistochemical, and ultrastructural analyses were conducted. The patients ranged in age from 50 to 73 years (mean age, 65 years) with preoperative serum prostate-specific antigen levels ranging from 2.7 to 37.5 ng/mL (mean, 15.2 ng/mL). All six cases were bilateral high-volume tumors. Five of six patients had high-grade tumors with extraprostatic extension. The foamy tumor cells were negative for mucin and lipid stains, but were positive for colloidal iron and Alcian blue stain. Ultrastructurally, the foamy cells displayed numerous intracytoplasmic vesicles and numerous polyribosomes. The authors conclude that the foamy appearance of these tumor cells is the result of the presence of numerous intracytoplasmic vesicles, and not the result of the presence of lipid or neutral mucin. This study illustrates that foamy gland carcinoma is a distinctive histologic variant of prostatic adenocarcinoma and is often associated with an aggressive behavior despite its deceivingly benign histologic appearance.

[Mucinous carcinoma of the prostate: critical review of Elbadawi's criteria]

OBJECTIVES

We present our experience on prostatic mucinous adenocarcinoma and at once we practice an actualization and a critical review of Elbadawi's criteria.

METHODS

After reviewing 206 prostatic carcinomas diagnosed in our hospital, we describe one case that fulfill criteria for being considered a prostatic mucinous adenocarcinoma. We also carry out a wide literature review trying to define anew the including criteria of this tumour by the light of modern knowledge and technology.

CONCLUSIONS

We think that for accepting a tumour as a prostatic mucinous adenocarcinoma, this have to fulfill the following criteria: 1. "More than 25% of a significative tumoral sample is mucinous pattern and present, single or clustered, tumour cells floating in immunohistochemically probed, acidic and neutral, mucin lakes". 2. "Tumour is Gleason 3-4 cribiform pattern with direct transition to colloid areas and usually coexist with classic adenocarcinoma but papillary growth patterns should be excluded. Tumour may contain a moderate proportion of signet-ring cells". 3. "Immunohistochemical staining for PSA have to be strongly positive in both, cribiform and mucinous, areas". 4. "Those PSA nonreactive, or only focally positive, mucinous adenocarcinomas, could be labeled as prostatic only when local or distant mucinous carcinomas are ruled out".

Partial atrophy in prostate needle cores: another diagnostic pitfall for the surgical pathologist

We have seen in consultation a variant of atrophy, which is frequently confused with well-differentiated adenocarcinoma of the prostate. We have designated this entity as partial atrophy to distinguish it from its more common counterpart of fully developed atrophy. Partial atrophy is defined as benign prostate glands with relatively scant cytoplasm, yet the glands are not fully atrophic in that they do not appear basophilic at low magnification. Fifty-one cases of partial atrophy were identified (4 from Johns Hopkins Hospital, 47 from consultation). Within the partial atrophy focus, irregular (crinkled) nuclei were frequent in 23.5% and occasionally present in 33.3% of cases. Visible nucleoli were frequent in 25.4% of cases. Basal cells were not identifiable in 27.4% of cases or were hard to identify in 35.3% of cases. No intraluminal crystalloids or blue-tinged mucinous secretion was identified in partial atrophy. Adenocarcinoma or glands suspicious for cancer were present in other cores in 15.6% of cases. More fully developed atrophy was present in simultaneously obtained needle cores in 35.3% of cases. In the cases in which regular atrophy was the only coexisting condition, it was present within one 10x field from the partial atrophy in 22.2%, farther than one 10x field from the partial atrophy in 11.1%, and present in the same gland as the partial atrophy in 66.7%. Partial atrophy may be confused with low-grade adenocarcinoma because of the focus of crowded glands, irregular nuclei, and visible nucleoli. Clues for recognizing partial atrophy include relatively scant cytoplasm, distinct crinkled nuclei, pale cytoplasm similar to adjacent, more recognizably benign glands, and association with more fully developed benign atrophy.