Prostate adenocarcinomas aberrantly expressing p63 are molecularly distinct from usual-type prostatic adenocarcinomas

Aberrant expression of GATA3 in metastatic adenocarcinoma of the prostate: an important pitfall

AIMS

The distinction of high-grade prostate cancer (PCa) from poorly differentiated urothelial carcinoma (UC) can be somewhat challenging on clinical and morphological grounds alone, yet it is of great importance for prognostication and choice of treatment. GATA3 is a useful immunohistochemical marker to confirm urothelial origin. However, recent works report strong GATA3 immunoexpression in primary high-grade PCa. The aim of this study was to explore GATA3 expression specifically in metastatic PCa.

METHODS AND RESULTS

The pathology databases of four tertiary institutions were queried for cases of metastatic PCa. Available slides and clinical records were reviewed by experienced genitourinary pathologists. Prostatic markers (PSA, PSAP, NKX3.1) and GATA3 immunohistochemistry were performed. A total of 163 metastatic PCa cases were included. At least one prostate marker was positive in each case of non-regional distant metastasis, confirming prostatic origin. GATA3 strong staining was found in four (2.5%) cases: two liver, one bone and one non-regional lymph-node metastases. All four patients had Grade Group 5 PCa at the initial diagnosis. The metastatic prostatic adenocarcinomas were solid, either with no gland formation (n = 3) or with only focal cribriforming (n = 1).

CONCLUSIONS

To our knowledge, this is the first study exploring GATA3 expression specifically in metastatic PCa. Despite being infrequent, GATA3 positivity in high-grade PCa may lead to misdiagnosis, with clinical implications. We recommend a panel of immunohistochemical markers, both prostatic and urothelial, for ruling out UC, either in primary tumour samples or in the event of metastases of unknown primary, when a genitourinary origin is suspected.

Aggressive prostatic adenocarcinoma with urothelial-like morphology, with frequent CK7/CK20/HMWK expression and occasional diffuse neuroendocrine features: A clinicopathologic study of 12 cases

INTRODUCTION

Prostatic adenocarcinoma can occasionally display urothelial carcinoma morphology, which prompts immunohistochemistry (IHC) studies to determine its lineage. Typically, prostate cancer is characterized by the lack of cytokeratin (CK) 7, CK20 and high molecular weight keratin (HMWK) expression, as opposed to bladder cancer.

METHODS

We report a series of 12 prostatic adenocarcinoma cases with unusual urothelial-like morphology, diagnosed at two academic institutions in Toronto between 2018 and 2023, and analyzed by immunohistochemistry for prostatic, urothelial, and neuroendocrine marker expression. We collected patient age, androgen deprivation therapy (ADT) status, tumour site, histomorphology, Grade group (GG) and results of genetic testing.

RESULTS

The median age of the 12 patients included in this case series was 75.5 years (range 41-85). A history of prostatic cancer was noted in 7/12 (58%) patients. Five of nine (56%) patients had elevated serum PSA level at diagnosis. Six of eleven (55%) patients had prior ADT. Tumour sites were prostate (n = 6), bladder (n = 3), liver metastases (n = 2), and lung metastasis (n = 1). GGs of the primary tumours were GG3 (n = 1) and GG5 (n = 8). The observed urothelial-like morphology was diffuse in ten cases, and focal in two cases. CK7 was strong/diffuse in 8/11 tested cases, and focal weak in one case. CK20, HMWK, p63 and GATA3 were patchy/focal/weak/moderate in 3/6, 4/7, 4/8 and 2/9 cases, respectively. Ten (83%) cases were positive for at least one prostatic marker; eight (67%) cases had loss/weak staining of at least one prostatic marker. AR loss was seen in 2/7 (29%) cases. Seven of ten (70%) cases had diffuse/strong expression of at least one neuroendocrine marker. No trend was evident between prior ADT/AR status and any IHC result. Molecular analyses for DNA damage repair (DDR) genes (n = 6) demonstrated one ATM deletion (bladder). In addition, one TMPRSS2:ERG fusion (lung metastasis) was identified.

CONCLUSION

This series comprises high-grade and/or metastatic prostatic adenocarcinoma cases with distinctive urothelial-like morphology and frequent aberrant CK7/CK20/HMWK expression. Their histomorphology, highly suggestive of an urothelial origin, represents a diagnostic pitfall that can lead to considerable management repercussions. The fact that a high proportion of the reported cases had loss/weak expression of at least one of the tested prostatic-specific markers, and occasionally a diffuse positivity for neuroendocrine markers highlights the importance of (1) clinical history and (2) utilization of broad IHC panels to correctly diagnose such unusual prostate cancer cases.

The Application and Pitfalls of Immunohistochemical Markers in Challenging Diagnosis of Genitourinary Pathology

CONTEXT.—

The morphologic features of different entities in genitourinary pathology overlap, presenting a diagnostic challenge, especially when diagnostic materials are limited. Immunohistochemical markers are valuable when morphologic features alone are insufficient for definitive diagnosis. The World Health Organization classification of urinary and male genital tumors has been updated for 2022. An updated review of immunohistochemical markers for newly classified genitourinary neoplasms and their differential diagnosis is needed.

OBJECTIVE.—

To review immunohistochemical markers used in the diagnosis of genitourinary lesions in the kidney, bladder, prostate, and testis. We particularly emphasized difficult differential diagnosis and pitfalls in immunohistochemistry application and interpretation. New markers and new entities in the 2022 World Health Organization classifications of genitourinary tumors are reviewed. Recommended staining panels for commonly encountered difficult differential diagnoses and potential pitfalls are discussed.

DATA SOURCES.—

Review of current literature and our own experience.

CONCLUSIONS.—

Immunohistochemistry is a valuable tool in the diagnosis of problematic lesions of the genitourinary tract. However, the immunostains must be carefully interpreted in the context of morphologic findings with a thorough knowledge of pitfalls and limitations.

Basal epithelial cells in prostate development, tumorigenesis, and cancer progression

The prostate epithelium is composed of two predominant cell populations: luminal and basal epithelial cells. Luminal cells have a secretory function that supports male fertility while basal cells function in regeneration and maintenance of epithelial tissue. Recent studies in humans and mice have expanded our knowledge of the role and regulation of luminal and basal cells in prostate organogenesis, development, and homeostasis. The insights from healthy prostate biology can inform studies focused on the origins of prostate cancer, progression of the disease, and development of resistance to targeted hormonal therapies. In this review, we discuss a critical role for basal cells in the development and maintenance of healthy prostate tissue. Additionally, we provide evidence supporting a role for basal cells in oncogenesis and therapeutic resistance mechanisms of prostate cancer. Finally, we describe basal cell regulators that may promote lineage plasticity and basal cell identity in prostate cancers that have developed therapeutic resistance. These regulators could serve as therapeutic targets to inhibit or delay resistance and thereby improve outcomes for prostate cancer patients.

Novel Histopathological Biomarkers in Prostate Cancer: Implications and Perspectives

Prostate cancer (PCa) is the second most frequently diagnosed cancer in men. Despite the significant progress in cancer diagnosis and treatment over the last few years, the approach to disease detection and therapy still does not include histopathological biomarkers. The dissemination of PCa is strictly related to the creation of a premetastatic niche, which can be detected by altered levels of specific biomarkers. To date, the risk factors for biochemical recurrence include lymph node status, prostate-specific antigen (PSA), PSA density (PSAD), body mass index (BMI), pathological Gleason score, seminal vesicle invasion, extraprostatic extension, and intraductal carcinoma. In the future, biomarkers might represent another prognostic factor, as discussed in many studies. In this review, we focus on histopathological biomarkers (particularly CD169 macrophages, neuropilin-1, cofilin-1, interleukin-17, signal transducer and activator of transcription protein 3 (STAT3), LIM domain kinase 1 (LIMK1), CD15, AMACR, prostate-specific membrane antigen (PSMA), Appl1, Sortilin, Syndecan-1, and p63) and their potential application in decision making regarding the prognosis and treatment of PCa patients. We refer to studies that found a correlation between the levels of biomarkers and tumor characteristics as well as clinical outcomes. We also hypothesize about the potential use of histopathological markers as a target for novel immunotherapeutic drugs or targeted radionuclide therapy, which may be used as adjuvant therapy in the future.

Expression of high molecular weight cytokeratin-A novel feature of aggressive and innate hormone-refractory prostatic adenocarcinoma

BACKGROUND

Castration-resistance is common in advanced prostatic adenocarcinomas (PACs) treated with androgen deprivation therapy (ADT) and usually occurs after 2 years following treatment. A minority of PACs confer innate ADT resistance without prior hormonal treatment. The expression of HMWCK in PAC cells has not been studied. This study aimed to investigate the clinicopathologic and genomic features of HMWCK-expressing PACs and the relationship to ADT resistance.

METHODS

A total of 469 PACs were studied for HMWCK expression (39 postradiotherapy, 57 post-ADT, 373 treatment-naïve PACs). Clinicopathologic correlations of the HMWCK expression with tumor grade groups, specific tumor morphologies, tumor stages and disease recurrence/persistence/progression were performed. Five HMWCK⁺ PACs were also sequenced for genetic alterations.

RESULTS

Thirty one of the 469 cases (6.6%) showed variable HMWCK⁺ PAC. The HMWCK⁺ PAC often focally presented in the tumor and vast majority were associated with high Gleason scores and unfavorable growth patterns (cribriform, comedo-necrosis, and intraductal carcinoma) as well as high tumor stages. A small percentage of the HMWCK⁺ PCA (2/31, 6.5%) presented with frank squamous histomorphology. Vast majority (22/31, 87%) had no history of prior ADT. The HMWCK⁺ PAC all displayed diminished to lost expression of AR/NKX3.1. Most of the cases progressed within 12 months of ADT or disease persisted despite ADT. Of the 5 HMWCK⁺ PACs subjected to gene sequencing, 4 presented with PTEN/PI3K/MAPK pathway alterations.

CONCLUSION

The study demonstrated HMWCK⁺ PAC to be a novel type of innate ADT-resistant PAC. Overexpression of HMWCK in PAC can be potentially used as a surrogate biomarker for aggressive and innate hormone-refractory PACs. The genetic alterations imply potential therapeutic implications of PI3K/MAPK inhibitors in the treatment of these deadly diseases.

Prostate Cancer: Update on Grading and Reporting

The Gleason scoring system and Grade Group systems facilitate accurate grading and reporting of prostate cancer, which are essential tasks for surgical pathologists. Gleason Pattern 4 is critical to recognize because it signifies a risk for more aggressive behavior than Gleason Pattern 3 carcinoma. Prostatic adenocarcinoma with radiation or androgen therapy effect, with aberrant P63 expression, or with Paneth cell-like differentiation represent pitfalls in prostate cancer grading because although they display architecture associated with aggressive behavior in usual prostatic adenocarcinoma, they do not behave aggressively and using conventional Gleason scoring in these tumors would significantly overstate their biologic potential.

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.

Aberrant Expression of p63 in an Adenocarcinoma of the Prostate That Has Metastasized to the Oral Cavity

Metastasis specifically to the oral cavity is uncommon in cases of prostate adenocarcinoma. Only 4% of prostate cancer patients present with metastases to the oral cavity originating from the prostate. In the oral cavity, the mandible is the primary site of metastases. p63 is said to be a reliable marker to distinguish benign from malignant lesions of prostate origin, with benign lesions staining positive and malignant lesions staining negative. However, in rare instances, malignant prostate lesions have shown aberrant expression of p63. This case report highlights such a rare incidence of metastasis of prostate adenocarcinoma to the oral cavity involving the right buccal mucosa and the right side of the mandible and having an aberrant expression of p63 in a 76-year-old Chinese male. A computed tomography (CT) scan and bone scan revealed multiple bone metastases, and in three months, the patient succumbed to the disease. Thus, p63 is not exclusively expressed in benign lesions of the prostate, as the aberrant expression may also be evident in malignant lesions such as prostate adenocarcinoma. Therefore, the determination of benign or malignant lesions of the prostate using p63 must be interpreted with caution.

GSTP1 positive prostatic adenocarcinomas are more common in Black than White men in the United States

GSTP1 is a member of the Glutathione-S-transferase (GST) family silenced by CpG island DNA hypermethylation in 90-95% of prostate cancers. However, prostate cancers expressing GSTP1 have not been well characterized. We used immunohistochemistry against GSTP1 to examine 1673 primary prostatic adenocarcinomas on tissue microarrays (TMAs) with redundant sampling from the index tumor from prostatectomies. GSTP1 protein was positive in at least one TMA core in 7.7% of cases and in all TMA cores in 4.4% of cases. The percentage of adenocarcinomas from Black patients who had any GSTP1 positive TMA cores was 14.9%, which was 2.5 times higher than the percentage from White patients (5.9%; P < 0.001). Further, the percentages of tumors from Black patients who had all TMA spots positive for GSTP1 (9.5%) was 3-fold higher than the percentage from White patients (3.2%; P<0.001). In terms of association with other molecular alterations, GSTP1 positivity was enriched in ERG positive cancers among Black men. By in situ hybridization, GSTP1 mRNA expression was concordant with protein staining, supporting the lack of silencing of at least some GSTP1 alleles in GSTP1-positive tumor cells. This is the first report revealing that GSTP1-positive prostate cancers are substantially over-represented among prostate cancers from Black compared to White men. This observation should prompt additional studies to determine whether GSTP1 positive cases represent a distinct molecular subtype of prostate cancer and whether GSTP1 expression could provide a biological underpinning for the observed disparate outcomes for Black men.

Aberrant GATA3 Staining in Prostatic Adenocarcinoma: A Potential Diagnostic Pitfall

Distinguishing between poorly differentiated urothelial carcinoma and high-grade prostatic adenocarcinoma is a common challenge in genitourinary pathology, particularly when the tumor involves the bladder neck or prostatic urethra. Clinically, the distinction between these 2 tumors can also be difficult. Proper diagnosis in these patients is essential as they have differing prognoses and clinical management. GATA3 is thought to be a sensitive and relatively specific marker of urothelial carcinoma. However, there is scant data regarding GATA3 labeling of high-grade prostatic adenocarcinoma. The aim of this study is to describe rare cases with strong aberrant GATA3 staining in prostatic adenocarcinoma as a potential diagnostic pitfall. We identified 9 cases of prostatic adenocarcinoma with aberrant positive GATA3 staining from 2015 to 2020 as part of a large consultation service at our institution. All 9 cases were grade group 5, 8 had a Gleason score of 5+5=10 and 1 had a score of 4+5=9. Five of the cases were from the prostate, 3 from the urinary bladder, and 1 from the prostatic urethra. All cases were morphologically typical of high-grade prostatic adenocarcinoma, although were sent for consultation due to uncertainty in the diagnosis. GATA3 positivity was strong, diffuse in 4 cases; strong, patchy in 2 cases and strong, focal in 3 cases. All cases were positive for NKX3.1, 6 positive for p501s, and 6 positive for PSA, with 7/9 cases showing expression of at least 2 prostate-specific markers. The current study describes that rare cases of prostatic adenocarcinoma can show focal or diffuse strong staining for GATA3. In order to avoid this diagnostic pitfall, undifferentiated carcinomas involving the prostate, bladder neck, or trigone should be evaluated not only with GATA3 but also prostate-specific markers.

Molecular MR Imaging of Prostate Cancer

This review summarizes recent developments regarding molecular imaging markers for magnetic resonance imaging (MRI) of prostate cancer (PCa). Currently, the clinical standard includes MR imaging using unspecific gadolinium-based contrast agents. Specific molecular probes for the diagnosis of PCa could improve the molecular characterization of the tumor in a non-invasive examination. Furthermore, molecular probes could enable targeted therapies to suppress tumor growth or reduce the tumor size.

Prostate adenocarcinoma of secretory type with wide expression of p63 and negativity of the basal marker Ck5/6: Rare subtype of adenocarcinoma of secretory origin and to be differentiated from basal cell carcinoma. Review of literature

We report a case of prostate carcinoma with wide nuclear expression for p63. These cases are rare and show atypical cytoplasmic/membrane expression of Ck5/6, alpha-methylacyl coenzyme A racemase and high-molecular-weight cytokeratin. It is rare to find this type of carcinoma with negativity for Ck5/6. We would like to present this case to avoid a diagnostic pitfall and with review of literature to understand the origin of this rare subtype.

TAp63 and ΔNp63 (p40) in prostate adenocarcinomas: ΔNp63 associates with a basal-like cancer stem cell population but not with metastasis

Like other malignancies, prostate tumors are thought to contain cancer stem-like cells (CSCs) that are responsible for growth, metastasis, and therapy resistance. ΔNp63 (also called p40) is a regulator of normal prostate stem/progenitor cell activities and a marker of normal basal epithelial cells. The levels of ΔNp63 are reduced in prostate adenocarcinomas, although there is also evidence that ΔNp63 is involved in CSC regulation and drives metastasis to the bone. We studied metastatic deposits of prostate cancers with isoform-specific ΔNp63 and TAp63 antibodies. We identified p63-positive cells in only 3 of 42 metastatic prostate tumors (7%), including 2/38 (5.3%) "usual-type" adenocarcinomas. ΔNp63 and TAp63 isoforms were present in the nuclei of a small subpopulation (< 1%) of tumor cells in these metastases. ΔNp63-positive cells showed a basal-like cell phenotype (cytokeratin 8- and androgen receptor-negative, high molecular weight cytokeratin- and cytokeratin 19-positive), distinct from the tumor bulk. TAp63-positive cells were similar but were sometimes cytokeratin 8-positive. A subset of ΔNp63-positive tumor cells were CD44-positive, a marker of "basal" CSCs but were not positive for the "epithelial" CSC marker ALDH1. TAp63 was not associated with either of these CSC markers. None of the tumors containing p63-positive cells showed evidence of bone metastasis, compared with 28% of the p63-negative tumors. These data show that both ΔNp63 and TAp63 are present in only a small proportion of prostate adenocarcinomas and do not associate with metastasis. The data suggest heterogeneity of CSCs in prostate cancer, similar to other cancer types.

Integrated immunohistochemical and molecular analysis improves diagnosis of high-grade carcinoma in the urinary bladder of patients with prior radiation therapy for prostate cancer

Prostatic adenocarcinoma and urothelial carcinoma typically demonstrate distinct morphologic and immunohistochemical features. However, high-grade prostate and urothelial carcinomas sometimes show significant morphologic and immunohistochemical overlap, which can result in misdiagnosis and mistreatment. This diagnostic dilemma is particularly acute in patients previously treated with radiation and/or hormone therapy for prostate cancer, who later present with high-grade carcinoma in the urinary bladder. To address the diagnostic utility of integrated immunohistochemical and molecular analysis in this setting, we evaluated 25 high-grade carcinomas of the bladder for which morphologic features were deemed indeterminate. Our analysis included immunohistochemistry for urothelial markers (GATA3, p63, uroplakin II), prostate markers (NKX3.1, prostate specific antigen, P501S), androgen receptor (AR) and ERG, along with molecular characterization using capture-based next generation DNA sequencing. Immunohistochemical findings were concordant with the final integrated diagnosis in 21 (84%) cases. However, in three (12%) cases, immunohistochemistry supported a diagnosis of urothelial carcinoma, but molecular analysis identified the correct diagnosis of prostate cancer based on the presence of a TMPRSS2-ERG fusion. One case remained unclassifiable even after this integrated analysis. Notably, in 1 of 21 cases, the presence of a TERT promoter mutation and the absence of a TMPRSS2-ERG fusion would typically favor a diagnosis of urothelial carcinoma, but the aggregate immunohistochemical and molecular findings instead supported a diagnosis of microsatellite unstable prostatic adenocarcinoma with deep deletion of MSH2 and MSH6. Our findings highlight the importance of considering prostatic origin in high-grade carcinoma of the urinary bladder of patients with a history of treated prostate cancer, even when the immunohistochemical findings favor urothelial carcinoma. In a subset of cases, an approach that integrates immunophenotypic and molecular data may help correctly assign site of origin and prevent misdiagnosis that can result from overreliance on any individual immunohistochemical or molecular result.

Morphological and Immunohistochemical Biomarkers in Distinguishing Prostate Carcinoma and Urothelial Carcinoma: A Comprehensive Review

The differential diagnosis between high-grade prostate carcinoma and infiltrating urothelial carcinoma (UC) in transurethral resection prostate specimens as well as cystoprostatectomy specimens may often be challenging due to morphologic and clinical overlap of the 2 entities. Such distinction has critical therapeutic and staging consequences, yet it is hampered by both issues in morphology and by the low accuracy rates of single immunohistochemical markers, as reported in literature. This review aims to provide a comprehensive analysis of the available morphological and immunohistochemical parameters, which may allow to discriminate between prostate carcinoma and urothelial carcinoma in the proper clinical context and to discuss their diagnostic applications in daily practice.

Immunohistochemical Pitfalls in Genitourinary Pathology: 2018 Update

Immunohistochemistry may be a very useful adjunct to morphologic diagnosis in many areas of surgical pathology, including genitourinary pathology. In this review, we address common diagnostic dilemmas where immunophenotypic analysis may be utilized and we highlight pitfalls specific to each scenario. For prostate, we review the diagnosis of limited prostatic adenocarcinoma and the distinction of high-grade prostatic adenocarcinoma from urothelial carcinoma. We also cover markers of urothelial lineage in the diagnosis of metastatic carcinoma of unknown primary site. In the kidney, distinction of poorly differentiated renal cell carcinoma from urothelial carcinoma and epithelioid angiomyolipoma, adjuncts to the recognition of hereditary renal neoplasia, and the diagnosis of metastatic renal cell carcinoma are discussed. Finally, for testis we address distinction of germ cell tumors from sex cord-stromal tumors, as well as the diagnosis of metastatic germ cell tumors.

Transcriptional Regulation in Prostate Cancer

Prostate cancer development involves corruption of the normal prostate transcriptional network, following deregulated expression or mutation of key transcription factors. Here, we provide an overview of the transcription factors that are important in normal prostate homeostasis (NKX3-1, p63, androgen receptor [AR]), primary prostate cancer (ETS family members, c-MYC), castration-resistant prostate cancer (AR, FOXA1), and AR-independent castration-resistant neuroendocrine prostate cancer (RB1, p53, N-MYC). We use functional (in vitro and in vivo) as well as clinical data to discuss evidence that unveils their roles in the initiation and progression of prostate cancer, with an emphasis on results of chromatin immunoprecipitation followed by high-throughput sequencing (ChIP-seq).

ETS2 is a prostate basal cell marker and is highly expressed in prostate cancers aberrantly expressing p63

BACKGROUND

Rare prostate carcinomas aberrantly express p63 and have an immunophenotype intermediate between basal and luminal cells. Here, we performed gene expression profiling on p63-expressing prostatic carcinomas and compared them to usual-type adenocarcinoma. We identify ETS2 as highly expressed in p63-expressing prostatic carcinomas and benign prostate basal cells, with lower expression in luminal cells and primary usual-type adenocarcinomas.

METHODS

A total of 8 p63-expressing prostate carcinomas at radical prostatectomy were compared to 358 usual-type adenocarcinomas by gene expression profiling performed on formalin fixed paraffin embedded tumor tissue using Affymetrix 1.0 ST microarrays. Correlation between differentially expressed genes and TP63 expression was performed in 5239 prostate adenocarcinomas available in the Decipher GRID. For validation, ETS2 in situ hybridization was performed on 19 p63-expressing prostate carcinomas and 30 usual-type adenocarcinomas arrayed on tissue microarrays (TMA).

RESULTS

By gene expression, p63-expressing prostate carcinomas showed low cell cycle activity and low Decipher prognostic scores, but were predicted to have high Gleason grade compared to usual-type adenocarcinomas by gene expression signatures and morphology. Among the genes over-expressed in p63-expressing carcinoma relative to usual-type adenocarcinoma were known p63-regulated genes, along with ETS2, an ETS family member previously implicated as a prostate cancer tumor suppressor gene. Across several cohorts of prostate samples, ETS2 gene expression was correlated with TP63 expression and was significantly higher in benign prostate compared to usual-type adenocarcinoma. By in situ hybridization, ETS2 gene expression was high in benign basal cells, and low to undetectable in benign luminal cells or usual-type adenocarcinoma. In contrast, ETS2 was highly expressed in 95% (18/19) of p63-expressing prostate carcinomas.

CONCLUSIONS

ETS2 is a predominantly basally-expressed gene in the prostate, with low expression in usual-type adenocarcinoma and high expression in p63-expressing carcinomas. Given this pattern, the significance of ETS2 loss by deletion or mutation in usual-type adenocarcinomas is uncertain.

Immunohistochemical panel to characterize canine prostate carcinomas according to aberrant p63 expression

An unusual variant of prostate adenocarcinoma (PC) expressing nuclear p63 in secretory cells instead of the typical basal expression has been reported in men. Nevertheless, the biological behavior and clinical significance of this phenomenon is unknown. In dogs, this unusual PC subtype has not been described. In this study, p63 immunoexpression was investigated in 90 canine PCs and 20 normal prostate tissues (NT). The p63 expression pattern in luminal or basal cells was confirmed in a selected group of 26 PCs and 20 NT by immunohistochemistry and/or Western blotting assays. Eleven canine PC samples aberrantly expressing p63 (p63+) in secretory cells were compared with 15 p63 negative (p63-) cases in the context of several molecular markers (high molecular weight cytokeratin-HMWC, CK8/18, CK5, AR, PSA, chromogranin, NKX3.1, PTEN, AKT and C-MYC). P63+ samples were positive for CK5, HMWC and CK8/18 and negative for PSA, NKX3.1, PTEN and chromogranin. Five p63+ PCs were negative for AR, and the remaining six samples had low AR expression. In contrast, p63- PC showed AR and PSA positive expression in all 15 samples. Only five p63- PCs were positive for CK5. Both p63+ and p63- PC samples showed higher cytoplasmic AKT expression and nuclear C-MYC staining in comparison with normal tissues. Metastatic (N = 12) and non-metastatic (N = 14) PCs showed similar immunoexpression for all markers tested. In contrast to human PC, canine PC aberrantly expressing p63 showed higher expression levels of HMWC and CK5 and lower levels of NKX3.1. Canine p63+ PC is a very rare PC group showing a distinct phenotype compared to typical canine PC, including AR and PSA negative expression. Although in a limited number of cases, p63 expression was not associated with metastasis in canine PC, and cytoplasmic p63 expression was observed in animals with shorter survival time, similar to human PC cases.

Rapid Loss of RNA Detection by In Situ Hybridization in Stored Tissue Blocks and Preservation by Cold Storage of Unstained Slides

OBJECTIVES

Recent commercialization of methods for in situ hybridization using Z-pair probe/branched DNA amplification has led to increasing adoption of this technology for interrogating RNA expression in formalin-fixed, paraffin-embedded (FFPE) tissues. Current practice for FFPE block storage is to maintain them at room temperature, often for many years.

METHODS

To examine the effects of block storage time on FFPE tissues using a number of RNA in situ probes with the Advanced Cellular Diagnostic's RNAscope assay.

RESULTS

We report marked reductions in signals after 5 years and significant reductions often after 1 year. Furthermore, storing unstained slides cut from recent cases (<1 year old) at -20°C can preserve hybridization signals significantly better than storing the blocks at room temperature and cutting the slides fresh when needed.

CONCLUSIONS

We submit that the standard practice of storing FFPE tissue blocks at room temperature should be reevaluated to better preserve RNA for in situ hybridization.

Usefulness of GATA-3 as a marker of seminal epithelium in prostate biopsies

OBJECTIVES

The incidental presence of seminal vesicle epithelium in prostate needle biopsies is generally recognisable through routine microscopy. However, the biopsy can sometimes be erroneously interpreted as malignant due to its architectural and cytological characteristics, and immunohistochemistry can be useful for correctly identifying the biopsy. Our objective was to analyse the potential usefulness of GATA-3 as a marker of seminal epithelium.

MATERIAL AND METHODS

Through immunohistochemistry with a monoclonal anti-GATA-3 antibody (clone L50-823), we studied seminal vesicle sections from 20 prostatectomy specimens, 12 prostate needle biopsies that contained seminal vesicle tissue and 68 prostate biopsies without seminal vesicle epithelium, 36 of which showed adenocarcinoma.

RESULTS

Staining for GATA-3 was intense in the 20 seminal vesicles of the prostatectomy specimens and in the 12 prostate needle biopsies that contained seminal epithelium. In the 60 biopsies without a seminal vesicle, GATA-3 was positive in the prostate basal cells and even in the secretory cells (57 cases), although with less intensity in 55 of the cases. One of the 36 prostatic adenocarcinomas tested positive for GATA-3.

CONCLUSIONS

The intense immunohistochemical expression of GATA-3 in the seminal vesicle epithelium can help identify the epithelium in prostate biopsies. This marker is also positive in the basal cells of healthy prostates and, with less intensity, in the secretory cells. Positivity, weak or moderate, is observed on rare occasions in prostatic adenocarcinomas.

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.

DNA methylation and histone modifications as epigenetic regulation in prostate cancer (Review)

Prostate cancer is the second most commonly diagnosed cancer in men in Poland after lung cancer and the third leading cause of cancer-related mortality after lung and colon cancer. The etiology of most cases of prostate cancer are not fully known, and therefore it is essential to search for the molecular basis of prostate cancer and markers for the early diagnosis of this type of cancer. Epigenetics deals with changes in gene expression that are not determined by changes in the DNA sequence. Epigenetic changes refer to changes in the structure of DNA, which are the result of DNA modification after replication and/or post-translational modification of proteins associated with DNA. In contrast to mutations, epigenetic changes are reversible and occur very rapidly. The major epigenetic mechanisms include DNA methylation, modification of histone proteins, chemical modification and chromatin remodeling changes in gene expression caused by microRNAs (miRNAs). Epigenetic changes play an important role in malignant transformation and can be specific to types of cancers including prostate cancer.

T-cadherin in prostate cancer: relationship with cancer progression, differentiation and drug resistance

Prostate cancer represents the second leading cause of cancer-related death in men. T-cadherin (CDH13) is an atypical GPI-anchored member of the cadherin family of adhesion molecules. Its gene was reported to be downregulated in a small series of prostate tumours. T-cadherin protein expression/localisation in prostate tissue has never been investigated. The purpose of our study was to analyse CDH13 gene and protein levels in large sets of healthy and cancer prostate tissue specimens and evaluate CDH13 effects on the sensitivity of prostate cancer cells to chemotherapy. Analysis of CDH13 gene expression in the TCGA RNAseq dataset for prostate adenocarcinoma (N = 550) and in tissue samples (N = 101) by qPCR revealed weak positive correlation with the Gleason score in cancer and no difference between benign and malignant specimens. Immunohistochemical analysis of tissue sections (N = 12) and microarrays (N = 128 specimens) demonstrated the presence of CDH13 on the apical surface and at intercellular contacts of cytokeratin 8-positive luminal cells and cells double-positive for cytokeratin 8 and basal marker p63. T-cadherin protein expression was markedly upregulated in cancer as compared to benign prostate hyperplasia, the increase being more prominent in organ-confined than in advanced hormone-resistant tumours, and correlated negatively with the Gleason pattern. T-cadherin protein level correlated strongly with cytokeratin 8 and with an abnormal diffuse/membrane localisation pattern of p63. Ectopic expression of CDH13 in metastatic prostate cancer cell line DU145 reduced cell growth in the presence of doxorubicin. We conclude that CDH13 protein, but not its gene expression, is strongly upregulated in early prostate cancer, correlates with changes in luminal/basal differentiation and p63 localisation, and promotes sensitivity of cancer cells to doxorubicin. These data identify CDH13 as a novel molecule relevant for prostate cancer progression and response to therapy.

The pathology of unusual subtypes of prostate cancer

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

Large oncosomes contain distinct protein cargo and represent a separate functional class of tumor-derived extracellular vesicles

Large oncosomes (LO) are atypically large (1-10μm diameter) cancer-derived extracellular vesicles (EVs), originating from the shedding of membrane blebs and associated with advanced disease. We report that 25% of the proteins, identified by a quantitative proteomics analysis, are differentially represented in large and nano-sized EVs from prostate cancer cells. Proteins enriched in large EVs included enzymes involved in glucose, glutamine and amino acid metabolism, all metabolic processes relevant to cancer. Glutamine metabolism was altered in cancer cells exposed to large EVs, an effect that was not observed upon treatment with exosomes. Large EVs exhibited discrete buoyant densities in iodixanol (OptiPrep^TM) gradients. Fluorescent microscopy of large EVs revealed an appearance consistent with LO morphology, indicating that these structures can be categorized as LO. Among the proteins enriched in LO, cytokeratin 18 (CK18) was one of the most abundant (within the top 5^th percentile) and was used to develop an assay to detect LO in the circulation and tissues of mice and patients with prostate cancer. These observations indicate that LO represent a discrete EV type that may play a distinct role in tumor progression and that may be a source of cancer-specific markers.

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.

PTEN loss and ERG protein expression are infrequent in prostatic ductal adenocarcinomas and concurrent acinar carcinomas

BACKGROUND

Prostatic ductal adenocarcinoma is an unusual and aggressive morphologic subtype of prostate cancer. PTEN gene deletion and ERG gene rearrangement are among the most common genomic changes in acinar prostate cancers. Though ductal adenocarcinoma most commonly occurs with synchronous usual-type acinar adenocarcinoma, little is known about the molecular phenotype of these mixed tumors.

METHODS

We used genetically validated immunohistochemistry (IHC) assays to assess PTEN and ERG status in a group of 37 surgically treated ductal adenocarcinomas and 18 synchronous acinar adenocarcinomas where we have previously reported ERG gene rearrangement status by fluorescence in situ hybridization (FISH). A group of 34 stage and grade-matched pure acinar adenocarcinoma cases was studied as a control.

RESULTS

ERG IHC was highly concordant with ERG FISH results, with 100% (36/36) concordance among ductal adenocarcinomas and 91% (31/34) concordance among 34 pure acinar carcinomas. Similar to previous FISH results, ERG expression by IHC was significantly less common among ductal adenocarcinomas (11% or 4/37) and their synchronous acinar tumors (6% or 1/18) compared to matched pure acinar adenocarcinoma cases (50% or 17/34; P = 0.0005 and 0.002, respectively). PTEN loss by IHC was also less common among ductal adenocarcinomas (18% or 6/34) and their synchronous acinar tumors (22% or 4/18) compared to matched pure acinar carcinomas (50% or 17/34; P = 0.01 and 0.08, respectively). As expected, PTEN loss was enriched among ERG positive compared to ERG-negative tumors in the pure acinar tumor control group (2.5-fold enrichment; P = 0.04) however this was not observed among the ductal adenocarcinomas (1.5 fold enrichment; P = NS). Of ductal adenocarcinomas with an evaluable synchronous acinar component, ERG status was concordant in 94% (17/18) and PTEN status was concordant in 94% (16/17).

CONCLUSIONS

Based on PTEN and ERG, ductal adenocarcinomas and their concurrent acinar carcinomas may be clonally related in some cases and show important molecular differences from pure acinar carcinoma.