攝護腺尿道原發惡性黑色素瘤：罕見病例報告與文獻回顧 

王大齊¹、溫玉清^1,2、邱宗傑³、林雍偉^1＊

臺北市立萬芳醫院 泌尿科¹ 臺北醫學大學 醫學院 泌尿學科²臺北市立萬芳醫院 內科部 血液腫瘤科³

Primary Malignant Melanoma of Prostatic Urethral: A Rare Case Report and Literature Review 

Ta-Chyi Wang¹, Yu-Ching Wen^1,2, Tzeon-Jye Chiou³, Yung-Wei Lin¹

1 Department of Urology, Wan Fang Hospital, Taipei Medical University

2 Department of Urology, School of Medicine, College of Medicine, Taipei Medical University

3 Division of Hematology and Medical Oncology, Department of Internal Medicine, Wan Fang Hospital, Taipei Medical University

Malignant melanoma is the most serious type of skin cancer but less common than squamous cell and basal cell types. The five-year survival rate of localized disease is up to 99% if under treatment. Primary melanoma of the genitourinary tract accounts for 0.2%~1% of all melanoma but represent an aggressive entity. Primary malignant melanoma of the prostatic is also very rare and most originated from prostate urethra. The neoplasm is extremely invasive and fatal, even early detection cases received radical prostatectomy, and rapid recurrence and metastasis occurs. Treatment options include systemic chemotherapy, targeted therapy if positive BRAF mutation or immunotherapy for metastatic diseases.  An averaged median survival of  28.6  months after diagnosis is noted. Here we present an 80-year-old man with a history of colon cancer status post concurrent chemo-radiotherapy and right hemicolectomy. He underwent medical treatment for lower urinary tract symptoms for years. Sudden onset of painless gross hematuria with blood clot bothered him for a week before diagnosis. Serum PSA level within normal range was found. Cystoscopy showed a black plaque lesion with an active bleeding, which ranged from the prostatic urethra to the bladder neck. The pathology of the prostatic urethral biopsy specimen is characterized by malignant melanoma composed of neoplastic melanocytic cells bearing moderately pleomorphic nuclei, prominent nucleoli with melanin pigmentation. Transurethral laser prostatectomy was performed to resolve bladder outlet obstruction and urethral bleeding, and residual black pigmented lesions located at the membranous urethra. Further image evaluation included PET-CT, which revealed multiple lung metastases. Mutation of BRAF was not detected. Systemic treatment with pembrolizumab was administered subsequently. Regression of lung metastases in terms of size and number was found in follow-up of CT. Currently, there is no standard treatment for prostatic urethral melanoma under a high tendency for early metastases and poor prognosis. In advanced disease, immunotherapy seemed transient promising in disease control.