Answer: Hormone treated prostate cancer

Histology: On further inquiry, it was discovered that this patient had received hormone therapy (Luprolide) before prostatectomy. While there were foci of usual prostatic adenocarcinoma within the specimen, the majority of the carcinoma had an atrophic appearance. Single cells with clear cytoplasm infiltrated between atrophic benign prostatic glands. These cells had bland, round nuclei and pale cytoplasm. In other areas, thin wisps of blue mucin were identified within the stroma, with intact nuclei being difficult to identify. These cells extended out of the prostate anteriorly to the level of the periprostatic fat.

Discussion: The bland appearance of these cells simulates that of histiocytes. The clinical history, the infiltrative pattern of the atrophic cancer, and the more recognizable atrophic cancer’s appearance help make this distinction. If necessary, stains for cytokeratin CAM5.2 or PSA can delineate the tumor cells. Malakoplakia is rare in the prostate. It is characterized by macrophages with calcified, iron-encrusted lysosomes, also known as Michaelis-Gutmann bodies. Periprostatic paraganglia can closely simulate hormonally treated cancer. These cells label for neuroendocrine markers like chromogranin, and are surrounded by S-100 positive sustentacular cells. They do not label for cytokeratin as prostatic adenocarcinomas do.

In general, one can use stains for low molecular weight cytokeratin (CAM5.2) to delineate the extent of the cancer. Staining a sequential section with high molecular weight cytokeratin 903 can help demonstrate that the single cells are unaccompanied by basal cells, and therefore represent carcinoma.