Basal cell hyperplasia in the peripheral zone of the prostate

Genomic Characterization of Prostatic Basal Cell Carcinoma

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

High Keratin-7 Expression in Benign Peri-Tumoral Prostatic Glands Is Predictive of Bone Metastasis Onset and Prostate Cancer-Specific Mortality

BACKGROUND

New predictive biomarkers are needed to accurately predict metastasis-free survival (MFS) and cancer-specific survival (CSS) in localized prostate cancer (PC). Keratin-7 (KRT7) overexpression has been associated with poor prognosis in several cancers and is described as a novel prostate progenitor marker in the mouse prostate.

METHODS

KRT7 expression was evaluated in prostatic cell lines and in human tissue by immunohistochemistry (IHC, on advanced PC, n = 91) and immunofluorescence (IF, on localized PC, n = 285). The KRT7 mean fluorescence intensity (MFI) was quantified in different compartments by digital analysis and correlated to clinical endpoints in the localized PC cohort.

RESULTS

KRT7 is expressed in prostatic cell lines and found in the basal and supra-basal compartment from healthy prostatic glands and benign peri-tumoral glands from localized PC. The KRT7 staining is lost in luminal cells from localized tumors and found as an aberrant sporadic staining (2.2%) in advanced PC. In the localized PC cohort, high KRT7 MFI above the 80th percentile in the basal compartment was significantly and independently correlated with MFS and CSS, and with hypertrophic basal cell phenotype.

CONCLUSION

High KRT7 expression in benign glands is an independent biomarker of MFS and CSS, and its expression is lost in tumoral cells. These results require further validation on larger cohorts.

Smoking Is Associated With Basal Cell Hyperplasia on Prostate Biopsy Specimens

OBJECTIVES

To the best of our knowledge, no study has analyzed the association between cigarette smoking and prostate basal cell proliferation. Therefore, we sought to evaluate whether smoking status is associated with the presence of basal cell hyperplasia (BCH).

METHODS

We performed a retrospective analysis of 8,196 men aged 50 to 75 years with prostate-specific antigen values between 2.5 µg/mL and 10 µg/mL and prior negative biopsy who were enrolled in the (REDUCE) trial. Cigarette smoking status was divided into current, former, or never categories at enrollment. The association between smoking and baseline BCH was evaluated, with logistic regression in univariable and multivariable analysis.

RESULTS

A total of 1,233 (15.1%) men were current smokers, 3,206 (39.1%) were former smokers, and 3,575 (45.8%) were never smokers. In univariable analysis, current smoking was associated with higher baseline BCH occurrence compared with never (odds ratio [OR], 1.87; 95% confidence interval [CI], 1.14-3.10) and former smokers (OR, 1.77; 95% CI, 1.06-2.95). Similar results were found after adjusting for patient characteristics (current vs never smokers: OR, 1.92; 95% CI, 1.14-3.26; current vs former smokers: OR, 1.71; 95% CI, 1.01-2.91).

CONCLUSIONS

Among men undergoing prostate biopsy, all of whom had a negative biopsy result, current smoking at enrollment was independently associated with BCH in standard peripheral zone prostate biopsies.

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 prostatic hyperplasia - what do we know?

OBJECTIVES

To present historical and contemporary hypotheses on the pathogenesis of benign prostatic hyperplasia (BPH), and the potential implications for current medical therapies.

METHODS

The literature on BPH was reviewed. BPH is a prevalent disease with significant health and economic impacts on patients and health organisations across the world, whilst the cause/initiation of the disease process has still not been fully determined.

RESULTS

In BPH, pathways involving androgens, oestrogens, insulin, inflammation, proliferative reawakening, stem cells and telomerase have been hypothesised in the pathogenesis of the disease. A number of pathways first described >40 years ago have been first rebuked and then have come back into favour. A system of an inflammatory process within the prostate, which leads to growth factor production, stem cell activation, and cellular proliferation encompassing a number of pathways, is currently in vogue. This review also highlights the physiology of the prostate cell subpopulations and how this may account for the delay/failure in treatment response for certain medical therapies.

CONCLUSION

BPH is an important disease, and as the pathogenesis is not fully understood it impacts the effectiveness of medical therapies. This impacts patients, with further research potentially highlighting novel therapeutic avenues.

Distinct expression patterns of SULT2B1b in human prostate epithelium

BACKGROUND

SULT2B1b (sulfotransferase family cytosolic 2B member 1b) catalyzes the sulfate conjugation of substrates such as cholesterol and oxysterols. Our laboratory has previously shown that SULT2B1b inhibition modulates androgen receptor signaling and induces apoptosis in prostate cancer cells. However, the functions of SULT2B1b in the prostate remain poorly understood.

METHODS

We characterized the expression pattern of SULT2B1b in human benign prostate hyperplasia (BPH) as well as prostate cancer to determine the relationship between SULT2B1b and prostate diseases, using immunohistochemistry, immunofluorescence staining, immunoblot, and real-time polymerase chain reaction.

RESULTS

SULT2B1b was strongly detected in the prostate epithelium but was absent in the stroma. Significantly lower SULT2B1b was found in primary cancer cells compared with adjacent normal epithelial cells. SULT2B1b further decreased in metastatic cancer cells. Most interestingly, we found, for the first time, that SULT2B1b was much more concentrated in the luminal layer than in the basal layer in both normal prostate and BPH samples. The stronger presence of SULT2B1b in luminal epithelial cells was confirmed by costaining with luminal and basal markers and in sorted paired luminal and basal cells. SULT2B1b expression was induced with prostate organoid differentiation.

CONCLUSIONS

SULT2B1b inversely correlates with prostate cancer status, with the highest level in the normal epithelium and lowest in the advanced metastatic prostate cancer. Furthermore, SULT2B1b is mostly located within the luminal layer of the prostate epithelium, suggesting that it may be implicated in luminal differentiation.

Basal Cells Show Increased Expression of Aromatase and Estrogen Receptor α in Prostate Epithelial Lesions of Male Aging Rats

Besides androgens, estrogen signaling plays a key role in normal development and pathologies of the prostate. Irreversible synthesis of estrogens from androgens is catalyzed by aromatase. Interestingly, animals lacking aromatase do not develop cancer or prostatitis, whereas those with overexpression of aromatase and, consequently, high estrogen levels develop prostatitis and squamous metaplasia via estrogen receptor 1 (ERα). Even with this evidence, the aromatase expression in the prostate is controversial. Moreover, little is known about the occurrence of age-dependent variation of aromatase and its association with histopathological changes commonly found in advanced age, a knowledge gap that is addressed herein. For this purpose, the immunoexpression of aromatase was evaluated in the prostatic complex of young adult to senile Wistar rats. ERα was also investigated, to extend our understanding of estrogen responsiveness in the prostate. Moderate cytoplasmic immunoreactivity for aromatase was detected in the glandular epithelium. Eventually, some basal cells showed intense staining for aromatase. The expression pattern for aromatase appeared similar in the normal epithelium when young and senile rats were compared; this result was corroborated by Western blotting. Conversely, in senile rats, there was an increase in the frequency of basal cells intensely stained for aromatase, which appeared concentrated in areas of intraepithelial proliferation and prostatitis. These punctual areas also presented increased ERα positivity. Together, these findings suggest a plausible source for hormonal imbalance favoring estrogen production, which, by acting through ERα, may favor the development of prostatic lesions commonly found in advanced age.

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.

Targeting phenotypic heterogeneity in benign prostatic hyperplasia

Benign prostatic hyperplasia and associated lower urinary tract symptoms remain difficult to treat medically, resulting in hundreds of thousands of surgeries performed annually in elderly males. New therapies have not improved clinical outcomes since alpha blockers and 5 alpha reductase inhibitors were introduced in the 1990s. An underappreciated confounder to identifying novel targets is pathological heterogeneity. Individual patients display unique phenotypes, composed of distinct cell types. We have yet to develop a cellular or molecular understanding of these unique phenotypes, which has led to failure in developing targeted therapies for personalized medicine. This review covers the strategic experimental approach to unraveling the cellular pathogenesis of discrete BPH phenotypes and discusses how to incorporate these findings into the clinic to improve outcomes.

Molecular pathogenesis of human prostate basal cell hyperplasia

BACKGROUND

Understanding the molecular pathogenesis of distinct phenotypes in human benign prostatic hyperplasia (BPH) is essential to improving therapeutic intervention. Current therapies target smooth muscle and luminal epithelia for relief of lower urinary tract symptoms (LUTS) due to BPH, but basal cell hyperplasia (BCH) remains untargeted. The incidence of has been reported at 8-10%, but a molecular and cellular characterization has not been performed on this phenotype.

METHODS

Using freshly digested tissue from surgical specimens, we performed RNA-seq analysis of flow cytometry-purified basal epithelia from 3 patients with and 4 patients without a majority BCH phenotype. qPCR was performed on 28 genes identified as significant from 13 non-BCH and 7 BCH specimens to confirm transcriptomic analysis. IHC was performed on several non-BCH and BCH specimens for 3 proteins identified as significant by transcriptomic analysis.

RESULTS

A total of 141 human BPH specimens were analyzed for the presence of BCH. Clinical characteristics of non-BCH and BCH cohorts revealed no significant differences in age, PSA, prostate volume, medical treatment, or comorbidities. Quantitation of cellular subsets by flow cytometry in 11 BCH patients vs. 11 non-BCH patients demonstrated a significant increase in the ratio of basal to luminal epithelia in patients with BCH (P <0.05), but no significant differences in the total number of leukocytes. RNA-seq data from flow cytometry isolated basal epithelia from patients with and without BCH were subjected to gene set enrichment analysis of differentially expressed genes, which revealed increased expression of members of the epidermal differentiation complex. Transcriptomic data were complemented by immunohistochemistry for members of the epidermal differentiation complex, revealing a morphological similarity to other stratified squamous epithelial layers.

CONCLUSIONS

Increased expression of epidermal differentiation complex members and altered epithelial stratification resembles the progression of other metaplastic diseases. These data provide insight into the plasticity of the human prostate epithelium and suggest a classification of basal cell hyperplasia as a metaplasia.

Low grade urothelial carcinoma mimicking basal cell hyperplasia and transitional metaplasia in needle prostate biopsy

PURPOSE

The vast majority of urothelial carcinomas infiltrating the bladder are consistente with high-grade tumors that can be easily recognized as malignant in needle prostatic biopsies. In contrast, the histological changes of low-grade urothelial carcinomas in this kind of biopsy have not been studied.

MATERIALS AND METHODS

We describe the clinicopathologic features of two patients with low-grade bladder carcinomas infiltrating the prostate. They reported dysuria and hematuria. Both had a slight elevation of the prostate specific antigen and induration of the prostatic lobes. Needle biopsies were performed. At endoscopy bladder tumors were found in both cases.

RESULTS

Both biopsies showed nests of basophilic cells and cells with perinuclear clearing and slight atypia infiltrating acini and small prostatic ducts. The stroma exhibited extensive desmoplasia and chronic inflammation. The original diagnosis was basal cell hyperplasia and transitional metaplasia. The bladder tumors also showed low-grade urothelial carcinoma. In one case, the neoplasm infiltrated the lamina propria, and in another, the muscle layer. In both, a transurethral resection was performed for obstructive urinary symptoms. The neoplasms were positive for high molecular weight keratin (34BetaE12) and thrombomodulin. No metastases were found in either of the patients, and one of them has survived for five years.

CONCLUSIONS

The diagnosis of low-grade urothelial carcinoma in prostate needle biopsies is difficult and may simulate benign prostate lesions including basal cell hyperplasia and urothelial metaplasia. It is crucial to recognize low-grade urothelial carcinoma in needle biopsies because only an early diagnosis and aggressive treatment can improve the prognosis for these patients.

Re-epithelialization resulted from prostate basal cells in canine prostatic urethra may represent the ideal healing method after two-micron laser resection of the prostate

The purpose of this study is to characterize the re-epithelialization of wound healing in canine prostatic urethra and to evaluate the effect of this re-epithelialization way after two-micron laser resection of the prostate (TmLRP). TmLRP and partial bladder neck mucosa were performed in 15 healthy adult male crossbred canines. Wound specimens were harvested at 3 days, and 1, 2, 3, and 4 weeks after operation, respectively. The histopathologic characteristics were observed by hematoxylin and eosin staining. The expression of cytokeratin 14 (CK14), CK5, CK18, synaptophysin (Syn), chromogranin A (CgA), uroplakin, transforming growth factor-β₁(TGF-β₁), and TGF-β type II receptor in prostatic urethra wound were examined by immunohistochemistry and real-time polymerase chain reaction, respectively. Van Gieson staining was performed to determine the expression of collagen fibers in prostatic urethra and bladder neck would. The results showed that the re-epithelialization of the prostatic urethra resulted from the mobilization of proliferating epithelial cells from residual prostate tissue under the wound. The proliferating cells expressed CK14, CK5, but not CK18, Syn, and CgA and re-epithelialize expressed uroplakin since 3 weeks. There were enhanced TGF-β₁ and TGF-β type II receptor expression in proliferating cells and regenerated cells, which correlated with specific phases of re-epithelialization. Compared with the re-epithelialization of the bladder neck, re-epithelialization of canine prostatic urethra was faster, and the expression of collagen fibers was relatively low. In conclusion, re-epithelialization in canine prostatic urethra resulted from prostate basal cells after TmLRP and this re-epithelialization way may represent the ideal healing method from anatomic repair to functional recovery after injury.

The benign mimickers of prostatic acinar adenocarcinoma

As the most frequent malignant histological subtype in prostatic cancer, prostatic acinar adenocarcinoma (PAA) has a series of benign mimickers including prostatic or non-prostatic lesions and normal structures, which may lead to an erroneous diagnosis and inappropriate treatment. It is very important to be aware of the existence of these mimickers and to recognize their histological features. The differential diagnosis should be based on a comprehensive evaluation of clinical history, histological structure, cytological morphology and the results of immunohistochemistry (IHC) staining, rather than on single criteria (e.g., the presence of prominent nucleoli or basal cell layer).

Basal cell hyperplasia (BCH) versus high grade prostatic intraepithelial neoplasia (HGPIN) in tiny prostatic needle biopsies: Unusual diagnostic dilemma

BACKGROUND

Histopathological differentiation between BCH and HGPIN in prostatic needle biopsies is a diagnostic challenge. The gold standard for detection of HGPIN and BCH is histopathological examination; however subjectivity in interpretation and tiny volume of obtained tissue hamper reliable diagnosis.

AIMS

The aim of this study was to assess usefulness of using the p63 and p504s to solve this problem. Although the use of p63 and p504s is now well established in differentiation between preneoplastic and neoplastic prostatic lesions, their usefulness in tiny tissue material is, however, not fully studied.

METHODS

The study included a spectrum of 30 prostatic needle biopsies (5 BCH, 10 HGPIN, 10 indefinite luminal proliferations where BCH and HGPIN could not be distinguished from each other and 5 adenocarcinomas). H&E stained sections were examined for histopathological features. Other sections were stained immunohistochemically with p63 and p504s.

RESULTS

The mean age of patients was 69 (SD=7.6) years. PSA range was 1.3-2.7 ng/ml. Ultrasongraphic findings were unremarkable. All BCH showed p504s-/p63+ pattern, All HGPIN had p504s+/p63+ pattern while carcinomas were p504s+/p63-. After immunostaining combined with histopathological features; the 10 indefinite specimens could be diagnosed as 4 BCH and 6 HGPIN. The article explains how applying this staining pattern on the challenging specimens, combined with histopathological features, can be helpful in proper identification of prostatic proliferations.

Histopathological spectrum of 364 prostatic specimens including immunohistochemistry with special reference to grey zone lesions

Purpose:

Prostatic lesions on routine staining sometimes cause a diagnostic dilemma, especially when malignant tissue is limited and is mixed with benign prostatic glands or because of the presence of benign mimickers of carcinoma. The application of immunohistochemistry contributes a valuable differential diagnosis. This study aimed to evaluate a complete spectrum of various prostatic lesions and to supplement the histopathological diagnosis with immunohistochemistry in suspicious or atypical cases.

Methods:

A total of 364 consecutive prostatic specimens were evaluated. Routine hematoxylin and eosin staining and immunohistochemical staining against 34βE12 cytokeratin and proliferative marker (alpha-methylacyl-CoA-racemase, AMACR) were performed by use of the peroxidase antiperoxidase method.

Results:

Benign prostatic hyperplasia was the most frequent finding and involved 285 patients (78.3%). Prostatitis (majority nonspecific) formed the predominant subgroup in nonneoplastic lesions (n=119, 32.7%). The incidence of carcinoma was low (n=73, 20.1%). Of the 26 atypical or suspicious cases, 18 cases were positive for high molecular weight cytokeratin (high molecular weight cytokeratin, HMWCK) only, 4 cases were positive for AMACR only, and 4 cases showed positivity for both HMWCK and AMACR.

Conclusions:

Biopsy remains the gold standard. However, as an adjunct to biopsy, proliferative markers and basal cell markers have value for resolving suspicious or atypical cases.

Nonneoplastic lesions of the prostate and bladder

CONTEXT

Specimens from the prostate and bladder are commonly encountered by the general surgical pathologist. Emphasis is usually placed on neoplasms of the bladder and prostate, particularly if malignant, owing to their therapeutic consequences. A good command of benign lesions occurring in the bladder and prostate, and knowledge of their preneoplastic potential will help pathologists confidently diagnose malignancy versus its benign mimickers and guide the urologists in choosing the appropriate therapy and follow-up for the patient.

OBJECTIVE

To present a mixture of benign entities, and discuss their histologic and clinical characteristics, hoping to provide a practical review for the general surgical pathologist.

DATA SOURCES

An extensive review of the literature on the entities discussed was performed.

CONCLUSIONS

A wide variety of benign entities are present in the prostate and bladder. Benign lesions in the prostate can be age related, such as prostatic atrophy and benign prostatic hyperplasia; transition zone associated, such as basal cell hyperplasia, adenosis, and sclerosing adenosis; or prostatic urethra associated. Benign lesions of the bladder encompass a wide variety of reactive changes that can occur in the urothelium, as well as hyperplastic lesions or reactive proliferations that could be misdiagnosed as malignant. The bladder responds to chronic irritation through several reactive/metaplastic lesions such as cystitis cystica/glandularis, keratinizing squamous metaplasia, or nephrogenic metaplasia. The urothelium can also give rise to hyperplastic/proliferative lesions, in particular von Brunn nest hyperplasia, papillary polypoid cystitis, and pseudocarcinomatous proliferation, which should be distinguished from malignant processes. Ectopic tissue, such as prostatic or mullerian, can also be seen.

Suppression of Tak1 promotes prostate tumorigenesis

More than 30% of primary prostate cancers contain a consensus deletion of an approximately 800 kb locus on chromosome 6q15.1. The MAP3K7 gene, which encodes TGF-β activated kinase-1 (Tak1), is a putative prostate tumor suppressor gene within this region whose precise function remains obscure. In this study, we investigated the role of Tak1 in human and murine prostate cancers. In 50 well-characterized human cancer specimens, we found that Tak1 expression was progressively lost with increasing Gleason grade, both within each cancer and across all cancers. In murine prostate stem cells and Tak1-deficient prostatic epithelial cells, Tak1 loss increased proliferation, migration, and invasion. When prostate stem cells attenuated for Tak1 were engrafted with fetal urogenital mesenchyme, the histopathology of the grafts reflected the natural history of prostate cancer leading from prostatic intraepithelial neoplasia to invasive carcinoma. In the grafts containing Tak1-suppressed prostate stem cells, p38 and c-jun-NH(2)-kinase activity was attenuated and proliferation was increased. Together, our findings functionally validate the proposed tumor suppressor role of Tak1 in prostate cancer.

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.

Prostatic basal cells in the peripheral and transitional zones: zonal variation in morphology and in immunophenotype

BACKGROUND

Benign prostatic hyperplasia and prostatic adenocarcinoma exhibit prominent zonal predilections. Basal cells from the transitional zone and from the peripheral zone are postulated to have different underlying biological properties. We studied basal cells in both prostatic zones.

METHODS

Tissue microarrays (TMA) were prepared from 65 whole-mounted prostatectomy specimens with prostatic adenocarcinoma. The transitional zone and peripheral zone were sampled from each prostate. TMA sections were stained with a basal cell cocktail (CK 34betaE12 + p63). The immunostaining pattern and the morphology of basal cells were recorded.

RESULTS

Triangular-shaped basal cells were highlighted by CK 34betaE12 cytoplasmic and p63 nuclear staining. These basal cells had their long axis oriented perpendicular to the basement membrane and their apex toward the lumen interdigited between secretory luminal cells. This morphology was seen in the majority of peripheral zone benign prostatic glands (92.0%) but only a minority of transitional zone benign prostatic glands (18.0%). Basal cells of the transitional zone showed weak or absent CK 34betaE12 staining in 65.9% of glands while maintaining p63. All glands with high-grade prostatic intraepithelial neoplasia (HGPIN) contained the triangular basal cells. In addition, basal cell clusters were identified in 8.7% of peripheral zone glands and 5.2% of HGPIN glands.

CONCLUSIONS

Our results indicate that the basal cell morphology and the basal cell immunophenotype have a zonal variation. The finding of a unique morphology of basal cells and the presence of basal cell clusters in the peripheral zone suggests that the peripheral zone might be the stem/progenitor cell-rich area in the human prostates.

Basal cell hyperplasia: an unusual diagnostic dilemma on prostate needle biopsies

Basal cell hyperplasia (BCH) is a well-recognized entity on transurethral resection specimens, but it is an uncommon finding on prostatic needle biopsies, and the diagnostic difficulties with it have not been fully defined on this material. A 13-year (1991-2003) retrospective review of the consult files of one of the authors was performed. In all cases, the focus of BCH was referred for consultation to rule out adenocarcinoma. Thirty-three cases of prominent BCH were identified. The dominant pattern of BCH consisted of either glands (26/33) or solid nests (7/33). Other minor patterns included cribriform (5), pseudocribriform (4), cords (1), and adenoid basal (1). Twelve of 33 cases showed an infiltrative pattern. Other features of BCH included prominent nucleoli (14/33), abnormal secretions (17/33 with dense pink and/or blue mucin), mitoses (6/33), altered stroma with increased cellularity (6/33), calcifications (6/33), intraluminal crystalloids (3/33) and perineural invasion (1/33). By immunohistochemistry, 7 (100%) out of 7 were positive for p63 and 14 (88%) of 16 were positive for high molecular weight cytokeratin. No cases (0/6) were positive for alpha-methylacyl-coenzyme A racemase. Basal cell hyperplasia, as a mimicker of cancer, is an uncommon entity encountered on prostatic needle biopsies. Helpful features for its diagnosis include solid nests, pseudocribriform glands, multilayering of cells, calcifications, and cellular stroma. Immunohistochemistry can be useful for documenting the basal cell layer and demonstrating negative racemase staining.

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.

Basal Cell Proliferations of the Prostate Other Than Usual Basal Cell Hyperplasia

Basaloid proliferations of the prostate with morphologic patterns other than usual basal cell hyperplasia are rare, and the distinction between benign and malignant lesions has been difficult. We describe 23 such lesions and classify them into two groups: adenoid cystic-like hyperplasia and adenoid cystic or basaloid carcinoma. Adenoid cystic-like hyperplasia (n = 19) was characterized by an older age at presentation (mean, 71.8 years), transition zone location with background of nodular hyperplasia, multifocality, lobulation, circumscription, and small acini with occasional hyalinization. A cribriform pattern limited to small- and medium-sized glands, squamous metaplasia, and hypercellular myxoid stroma were occasionally seen. Adenoid cystic carcinoma (n = 3) was characterized by a younger age at presentation (mean, 46.0 years), peripheral zone involvement, and large acini that were often dilated and exhibited extensive interanastomoses, prominent intraglandular hyalinization, perineural invasion, and extraprostatic extension. Basaloid carcinoma (n = 1) showed infiltration between normal glands, perineural invasion, and extraprostatic extension but lacked a cribriform architecture. The degree of cytologic atypia and mitotic rate overlapped between the hyperplasia and carcinoma cases. Both hyperplastic lesions and adenoid cystic carcinomas showed a basal cell phenotype with strong immunoreactivity to cytokeratins 14 and 34betaE12, but the basaloid carcinoma was negative for these markers. In all cases, the proliferating basal cells were nonreactive for myoepithelial and prostatic secretory cell markers. The 8 patients with adenoid cystic-like hyperplasia with available follow-up information had no progression of disease (mean follow-up period, 8.6 years). One patient with adenoid cystic carcinoma died with widespread metastases, but the 3 other patients with carcinomas had no disease progression (mean follow-up period, 7.0 years). In conclusion, most florid basaloid proliferations of the prostate fall into one of two categories. In the first, there is a clear association with nodular hyperplasia (adenoid cystic-like hyperplasia) and, although cytologic atypia and mitoses may be seen, they are present within a lesion that retains an orderly, vaguely nodular (noninfiltrative) pattern. The second group of cases (adenoid cystic and basaloid carcinoma) shows a widespread, haphazard infiltrative growth pattern. This study suggests that adenoid cystic carcinomas are biologically indolent following prostatectomy but have a low risk of distant metastasis.

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.