Prostasomes are a secretory product from the prostate. We aimed to investigate whether the distribution and amount of prostasomes in normal prostate epithelium were influenced by the dedifferentiation occurring in adenocarcinomas of the human prostate gland.

Transurethrally resected material from 11 patients with prostatic carcinoma of various malignancy grades, material from two lymph node metastases, and benign tissue from 10 total prostatectomies were subjected to immunohistochemical staining, using a mouse monoclonal antibody against human prostasomes (mAb 78).

Immunostaining of low‐grade carcinoma was similar to that of normal prostate gland which displayed a cytoplasmic granular staining of the apical (luminal) aspects of the secretory epithelial cells. In moderately well and poorly differentiated adenocarcinoma, the amount of stained components decreased, and the staining pattern became more heterogeneous. In multilayered glandular structures, the staining was concentrated at the lumen, leaving most other cells negative. The neoplastic cells of lymph node metastases of prostate carcinoma differed in amount and distribution of immunostained prostasomes.

The antigen recognized in the prostasomes by mAb78 was expressed in benign prostate tissue, prostate cancer, and to a lesser degree in lymph node metastases. There was a tendency towards decreased expression with increasing tumor grade. Prostate 39:36–40, 1999. © 1999 Wiley‐Liss, Inc.