Foamy gland carcinoma is a subtype of acinar adenocarcinoma characterized by foamy appearance, large cytoplasm, pyknotic nuclei, inconspicuous nucleoli and infiltrative pattern. In this study, we investigated the histological features and the incidence of foamy gland carcinoma. We compared foamy gland carcinoma with acinar adenocarcinoma according to age, prostate-specific antigen value, Gleason score, peripheral nerve invasion and accompanying high-grade prostatic intraepithelial neoplasia. Besides, we investigated the diagnostic value of immunohistochemical markers in foamy gland carcinoma. A total of 863 TRUS-guided prostate needle core biopsies performed at our hospital pathology clinic between January 1, 2010, and December 31, 2011, were examined, 251 of these were diagnosed acinar type adenocarcinoma. Conventional acinar type adenocarcinoma was present in 195 (78%) cases, and foamy gland carcinoma, in 56 cases (22%). We found that 11(19%) of the 56 foamy gland carcinoma cases were pure and 45 (81%) cases were mixed with conventional acinar type adenocarcinoma. Single-core localization was present in 7 of 14 pure foamy gland carcinomas, and the number of cases with a Gleason score of 7 and above was 21 (37%). No statistically significant difference was found between foamy gland carcinoma and conventional acinar type adenocarcinoma in terms of age, Gleason score, high-grade prostatic intraepithelial neoplasia, and prostate-specific antigen values. Peripheral nerve invasion was found to be statistically significantly more common in foamy gland carcinoma compared to acinar type adenocarcinoma (P < .05). The staining percentage of immunohistochemical markers in foamy gland carcinoma was 90.1% for p63, 90.6% for 34Beta 12 and 90.6% for AMACR. (C) 2014 Elsevier Inc. All rights reserved.