Phyllodes tumor of the prostate: a case report.

A case of prostatic phyllodes tumor which developed in a 78-yr-old man is reported. Histologically, the tumor comprised myxomatous and cellular portions with a proliferation of atypical stromal cells. Multinucleated giant cells were occasionally present, but mitoses were rare. Fibroblastic differentiation of the tumor cells was confirmed by numerous rough endoplasmic reticulums and free ribosomes, and by immunoreactivity for vimentin. Approximately one-third of the tumor cells showed estrogen-receptor immunoreactivity at their nuclei. The patient is well, with no evidence of tumor recurrence, five years after the resection. The tumor was diagnosed as being a benign prostatic phyllodes tumor showing fibroblastic differentiation, and of an estrogen-dependent nature.