Atypical sclerosing adenosis of the prostate: a rare mimic of adenocarcinoma

Abstract

Sclerosing adenosis of the prostate is a benign, small, acinar proliferation in dense spindle cell stroma, with a distinct immunohistochemical profiles. It is incidentally found in about 2% of transurethral resection specimens. The aim was to describe cases with significant cytological atypia mimicking cancer, which have not been previously reported. We describe five cases of sclerosing adenosis with significant cytological atypia, referred to as atypical sclerosing adenosis (ASA), which were initially considered suspicious or diagnostic of adenocarcinoma. Seven other cases of typical sclerosing adenosis were used as controls. All cases of typical and atypical sclerosing adenosis displayed an intact basal cell layer, which was immunoreactive for high-molecular-weight keratin, S100 protein, smooth muscle actin, and prostate-specific antigen, with no differences between ASA and the control group. Alpha-methylacyl-coenzyme A racemase was negative. Three of four cases of ASA had aneuploid DNA content by digital image analysis. All cases of typical sclerosing adenosis were diploid. During a mean follow-up of 33 months (range 5-73 months), none developed recurrence or prostatic cancer. ASA is an unusual small, acinar proliferation of the prostate that may be mistaken for adenocarcinoma, and should be distinguished from other mimics, including atypical adenomatous hyperplasia, mesonephric remnant hyperplasia, and post-atrophic hyperplasia. ASA is a benign lesion and aggressive treatment is unwarranted.