Prostate Metastasis of Malignant Melanoma
A 50-year-old male presented with complaints of lower urinary tract symptoms (LUTS) for 6 months and painless gross hematuria for 2 months. The results of a physical examination were completely normal, except for prominent prostatic enlargement detected by digital rectal examination. Three years ago he had been diagnosed as having malignant melanoma after a left axilla mass biopsy and had undergone wide local excision and left axillary node dissection. He was well for 2.5 years with a complete response to interferon treatment until his LUTS had started 6 months ago.\nPositron emission computed tomography screening of the body showed increased metabolic activity around the prostatic gland, and pelvic magnetic resonance imaging revealed a 10 cm×4 cm×8 cm prostatic mass lesion that displaced the rectum posterior and the sigmoid colon laterally (). Transrectal ultrasound-guided prostate biopsy was performed to rule out prostatic cancer and to diagnose the mass, although the prostate-specific antigen level was 0.2 ng/mL, which is consistent with a benign prostatic gland. The pathological diagnosis was reported as malignant melanoma infiltration of the prostatic gland. The patient subsequently underwent transurethral resection of the prostatic gland for symptomatic relief, and after resection of the normal prostatic gland layer, melanoma tissue was seen (). Pathologic examination with immunostaining with S-100, HMB45, and melanin-A confirmed the diagnosis of malignant melanoma (). At 6 months after the surgery, the patient died because of uncontrolled metastases of the melanoma to the liver and lung.