Malignant mesenchymoma of the prostate: immunohistochemical and ultrastructural observations.

A case of malignant mesenchymoma of the prostate is reported. Immunohistochemical and ultrastructural examination revealed malignant chondro-osteoblastic and rhabdomyoblastic features. A separate incidental prostatic adenocarcinoma was also seen. These lesions should be differentiated from carcinosarcoma in which adenocarcinoma is intermingled with malignant mesenchymal components.