Primary malignant melanoma of the male urethra: Case report and review of literature

INTRODUCTION: We report a rare case of primary malignant melanoma with inguinal lymph node metastasis in the male urethra. CASE PRESENTATION: A 57-year-old male patient presented with a small tumor on the ventral surface of the penis, which was discovered 5 months ago and did not cause pain or discomfort. In the past month, the patient has developed symptoms of urinary incontinence. MRI and PET/CT scans revealed a primary tumor in the penile urethra, but no metastases were found. The patient underwent partial penectomy surgery and laparoscopic bilateral inguinal lymphadenectomy within one month. The pathological combined with immunohistochemical staining confirmed primary malignant melanoma in the urethra with right inguinal lymph node metastasis. Despite complying with surgical and immunotherapy treatment with Pembrolizumab for 18 cycles, the patient was diagnosed with recurrent cancer in the penile stump after 05 months and he passed away after 18 months. DISCUSSION: Urethral melanoma is a rare and highly invasive type of cancer. It was often diagnosed at a late stage because the initial symptoms were not obvious in the lower urinary tract. Additionally, cancer progressed very quickly, making it difficult to treat. CONCLUSION: Urethral melanoma, if detected at a late stage with lymph node metastasis, has a significantly poor prognosis irrespective of the treatment method employed. However, to our best knowledge, very few publications can be found on this disease, and the strategic treatment remained unknown.