Answer: Basal cell hyperplasia and Clear cell cribriform hyperplasia

Histology: The section of prostate shows a proliferation of 2 different types of cribriform glands in the transition zone of the prostate. Some of the glands appear hyperchromatic on low power, and on higher magnification, one can see that the glands are lined by a layer of secretory cells with a proliferation of the underlying cells. These cells have characteristic nuclear features of basal cells, with oval to spindle shaped nuclei, lack of cytologic atypia and small nucleoli. The other cribriform glands consist of cells with clear cytoplasm and round nuclei without any cytologic atypia.

Discussion: This is an example of basal cell hyperplasia and clear cell cribriform hyperplasia. Although the basal cell hyperplasia appears hyperchromatic and stands out on low power, on higher magnification, one can see that the cells lack cytologic atypia and prominent nucleoli, thus ruling out high grade PIN. Basal cell hyperplasia, with the hyperplasic basal cells underlying the secretory cells, may be confused with urothelial carcinoma extending into prostatic ducts. However, urothelial carcinoma usually shows significant cytologic atypia, with large hyperchromatic cells. Urothelial cell metaplasia can also mimick basal cell hyperplasia, however, cribriforming architecture has not been described. In addition the cells of urothelial metaplasia usually show nuclear grooves. The use of cytokeratin 34betaE12 can help in difficult cases. High-molecular-weight cytokeratin shows multilayered and a continuous layer of staining of the basal cells in basal cell hyperplasia, while cribriform prostatic ntraepithelial neoplasia demonstrates an interrupted immunoreactive single cell layer of basal cells, and cribriform adenocarcinoma would be negative for high molecular weight cytokeratin.

The other type of cribriform glands seen in this case consist of clear secretory cells with small uniform round nuclei. Cribriform PIN and cribriform adenocarcinoma of the prostate would both show cytologic atypia with prominent nucleoli, which is lacking in these glands. High-molecular-weight cytokeratin would also show the presence of basal cells around these glands, differentiating them from cribriform adenocarcinoma.