Malignant cystic epithelial-stromal tumor of the prostate

A huge cystic tumor in the pelvis of a 62-year old man, cytologically by fine needle aspiration biopsy, was composed of malignant spindle cells and transitional as well as glandular epithelial cells. Histochemical, immunostaining, and ultrastructural studies of the aspirated specimens and on the radically resected tumor indicated that the neoplastic cells are of prostatic fibroleiomyomatous stromal and epithelial origin. The lesion did not extend to the urothelium of the urinary bladder. This tumor resembles the rare cystadenoleiomyofibroma of the prostate, yet the cytologic abnormalities suggest a malignant potential. Long-term follow-up and recognition of additional cases are necessary to define the biologic behavior of this neoplasm.