Primary melanoma of the prostate: case report and review of the literature.

Background: Primary melanoma of the prostate has an extremely rare incidence. Only five cases have been reported in the literature and prognosis is poor. The most likely origin of prostatic melanoma is the transitional epithelium of the prostatic urethra. Surgical care for primary melanoma of mucosal sites is less well established than for primary cutaneous melanoma, but excision of the primary is recommended if the patient has no systemic disease.
Case Presentation: Here, we describe a case of primary malignant melanoma of the prostate. A 37-year-old male patient with history of both chemo- and radiation therapy for Hodgkin's disease was admitted to the University Hospital Heidelberg on suspicion of pleomorphic sarcoma of the bladder. In-house diagnostic work-up revealed a malignant melanoma of the prostate. We then performed radical prostatectomy with extended lymphadenectomy. Despite presumably curative surgery, the patient suffered from early relapse of disease with pulmonary metastasis. Systemic chemotherapy and subsequent immuno-oncologic treatment was thereafter initiated.
Conclusion: Since prostatic melanoma is a rare disease and a melanoma metastasis of unknown primary is the differential diagnosis, a multidisciplinary approach including early imaging to rule out possible metastases and to search for another potentially existing primary is advisable. To prevent complications related to local tumor progression and to receive tissue for mutational analysis, we recommend complete surgical resection to reduce the tumor mass. Novel immune and targeted oncologic therapies can lead to an improved survival in some cases and support of clinical trials is needed.