Cystosarcoma phyllodes of the prostate. A pathologic and immunohistochemical study.

We treated two patients who had lesions in the prostate with histologic features similar to those of cystosarcoma phyllodes of the breast. In one case, the stroma progressed to a clearly sarcomatous appearance, whereas the other tumor had a cellular stroma that was mitotically inactive. This element was immunoreactive for vimentin and desmin in both cases but was negative for epithelial markers. In contrast, the epithelial component was immunoreactive for prostate-specific antigen and epithelial membrane antigen. Following surgical resection, both patients were well two and three years later, without local recurrence or distant metastasis. The histogenesis of these tumors is unknown.