Prostate cancer is the most common cancer in Australian men and pure ductal adenocarcinoma of the prostate (DAP) constitutes 1% of the cases. While DAP was initially thought to behave more indolently than acinar-type prostatic adenocarcinoma, it is now regarded as more aggressive, with a greater propensity to metastasise. There is however a paucity of literature relating to brain metastasis by the tumour. We report two cases of metastatic DAP to the brain which showed some positivity for CK7 and CK20 while negative and/or only focally positive for PSA and PSAP. The case reports also highlight a potential diagnostic pitfall in immunohistochemical interpretation of high grade prostate carcinomas with these four traditional antibodies. Pure prostate ductal adenocarcinoma, which by definition is Gleason score 4 + 4 = 8, may easily be overlooked in the differential diagnosis of metastatic brain tumours with cribriform, papillary, solid and/or complex glandular architecture if the immunohistochemistry is also misinterpreted.
(C) 2014 Royal College of Pathologists of Australasia