Cutaneous metastasis of prostatic adenocarcinoma: a cautionary tale.

With the exception of skin cancer, prostatic adenocarcinoma represents the most common cancer among men in the United States and the second most common cause of cancer mortality. Mortality is often associated with metastatic disease, which in the case of prostatic adenocarcinoma typically involves bones and only rarely affects the skin. Although clinical history and examination, laboratory tests and routine pathology can suggest the prostate as a source of metastatic disease, immunohistochemistry - specifically, for prostate-specific antigen (PSA) - is often used to help establish the diagnosis. We report a case of cutaneous metastatic prostatic adenocarcinoma presenting in the inguinal region of a 78-year-old man 5 years after his initial diagnosis. The case is unusual in that the clinical appearance mimicked a vascular proliferation and in that the metastatic prostatic adenocarcinoma failed to express PSA. Rather, expression of prostatic acid phosphatase was observed.