Poorly differentiated neuroendocrine carcinoma of the seminal vesicle.

We describe an extremely rare case of poorly differentiated neuroendocrine carcinoma arising from the seminal vesicle. A 67-year-old man presented with a left humeral bone tumor resulting in a pathological fracture. Positron emission tomography scan disclosed a large pelvic tumor mimicking prostatic cancer invading into the seminal vesicle. Laboratory data showed an elevation of neuron-specific enolase, despite the normal prostate-specific antigen. Transrectal needle biopsy showed a poorly differentiated carcinoma of the right seminal vesicle and the metastasis of the pelvic lymph node. Immunohistochemical results were compatible with the features of neuroendocrine carcinoma; synaptophysin, chromogranin A and CD 56 were positive. The previously biopsied bone tumor was finally diagnosed as a metastasis. A systemic chemotherapy using etoposide and cisplatin failed. The patient died of cancer one-and-a-half years later.