Answer: Clear cell cribriform hyperplasia

Histology: The area of interest consists of multiple cribriform glands. The sizes of these cribriform glands are approximately the same size as normal glands. Focally, these glands are more crowded and closely situated next to each other than seen with benign glands. At high magnification, the cells contain lightly eosinophilic cytoplasm. Nuclei appear uniformly benign. Focally, one can identify a clear row of basal cells beneath some of the glands.

Discussion: At low magnification, answers A, B and C would all be possible. In contrast, cribriform Gleason pattern 4 adenocarcinoma consists of large irregular cribriform nests. In contrast to both cribriform PIN and cribriform carcinoma, the lesion in the current case lacks cytologic atypia. Whereas with cribriform PIN and cribriform carcinoma one may see more benign appearing nuclei towards the center of the cribriform nest, at the periphery of the cribriform nest in cancer one typically sees enlarged nuclei with prominent nucleoli. Furthermore, one would not see a well-defined basal cell layer around cribriform carcinoma. Even with cribriform PIN where there is a patchy basal cell layer present, the basal cell layer is often inconspicuous and not as well defined as seen in the current case. The findings in the current case are classic for clear cell cribriform hyperplasia. Clear cell cribriform hyperplasia typically occurs within the transition zone and is more commonly seen on transurethral resections. In the current case, it may be that the needle biopsy is sampling the transition zone. Clear cell cribriform hyperplasia although mimicking a carcinoma and PIN is a totally benign entity and has no risk factor for development of carcinoma. It is controversial whether clear cell cribriform hyperplasia is a specific disease entity or rather a variant of cribriform benign prostatic hyperplasia. If one has trouble recognizing the basal cell layer, one can perform stains for high molecular weight cytokeratin which will rule out cribriform carcinoma. One cannot use this antibody to distinguish between cribriform PIN and clear cell cribriform hyperplasia.