Role of Immunohistochemistry in the Differentiation between Low Grade Prostatic Adenocarcinoma (Small Acinar Pattern) and Some Benign Mimickers

摘要

Background : prostatic adenocarcinoma is characterized by diverse architectural growth patterns and can be confused with some benign prostatic lesions. The most common pseudoneoplastic lesions in the prostate that can mimic low-grade prostatic adenocarcinoma are post-atrophic hyperplasia (PAH), atypical adenomatous hyperplasia (AAH) and sclerosing adenosis of the prostate (SAP). Objective: this study aimed to evaluate the histopathological and immunohistochemical features of some pseudoneoplastic lesions of the prostate that could potentially be confused with low-grade prostatic adenocarcinoma (small gland pattern). Material and Methods : 100 specimens of prostatic lesions were enrolled in this study and analyzed retrospectively (50 needle biopsy specimens and 50 transurethral resection of prostate (TURP) specimens). All cases had atypical foci that required further workup. Four slides per specimen were cut, one slide for hematoxylin and eosin stain (H&E) and the other 3 slides for immunohistochemical (IHC) staining by antibodies against 34E12 cytokeratin, p63 and alpha methyl acyl coenzyme A racemase (AMACR). Results: histological examination (prior to IHC staining) revealed provisional histological diagnosis of 35 cases of PAH, 12 cases of AAH, 13 cases of SAP and 40 cases of low grade prostatic adenocarcinoma. Immunohistochemical results revealed immunopositivity to 34E12 in a discontinuous pattern in 13 out of the 35 cases of PAH (13/35), immunopositivity to 34E12 and p63 in a continuous basal pattern in 17 cases (17/35) and negativity for all markers in 5 cases (5/35). 29 cases out of the 40 prostatic carcinomas showed immunopositivity for AMACR and negativity for 34E12 and p63 (29/40), 5 cases were negative for all markers (5/40) and 6 cases were positive to p63 and negative for AMACR and 34E12 (6/40). 8 out of the 12 cases diagnosed as AAH showed immunopositivity to 34E12 and p63 in a discontinuous pattern and negative to AMACR (8/12), 2 cases were positive to AMACR and negative to basal cell markers (2/12) and 2 cases were negative to all markers. All the 13 cases diagnosed histologically as SAP showed immunopositivity to 34E12 and p63 and immunonegativity to AMACR. Conclusion : immunohistochemistry (IHC) can be contributive in the diagnosis of prostatic adenocarcinoma if used with care and experience. No single marker can establish a diagnosis on its own, but interpretation must always be in conjunction with H&E morphology.