Metastatic malignant melanoma mimicking urinary bladder mass: A rare presentation

Abstract

Introduction. Melanoma is a solid aggressive tumor characterized by the malignant transformation of melanocytes. To date, only about 35 primary and about 30 metastatic malignant melanomas of the bladder have been reported. Our objective is to report a rare case of secondary tumor of urinary bladder. Case outline. A 57-year-old man presented to Urologic Clinic due to lower urinary tract symptoms. The urologist indicated transurethral resection (TUR). His medical history was significant for cutaneous malignant melanoma resected 3 years prior, which were localized at scapular region on the left side. Microscopic examination of the TUR specimen showed several fragments of ureter mucosa with presence of tumor and focally with normal urothel. Tumor cells were markedly atypical and polygonal in a solid pattern. The nuclei were large with variation in size and prominent eosinophilic nucleoli. Also, there were present areas with abundant brown pigment. Immunohistochemical analysis of tumor cells showed positivity for Melan A and HMB45 and negativity for GATA3. Molecular analysis showed that BRAF was mutated. Conclusion The incidence of malignant melanoma is high and increasing, but the urinary bladder is a rare location of metastasis. However, both primary and metastatic melanomas can occur in the bladder, so the urologist and the pathologist have to consider it when it is the primary site of onset, or when it represents the first symptomatic metastasis.