Primary malignant melanoma of urethra mimicking as urethral caruncle

Description 

A 50-year-old woman presented with dysuria and intermittent vaginal bleeding for last 6 months. On local examination, a 1x1 cm mass was seen protruding from anterior wall of urethral meatus. The mass was lobulated, firm, painless and tan coloured (figure 1). The local pelvic examination and general physical examination was normal. Cystourethroscopy revealed no abnormality in the urethra and urinary bladder. The mass was provisionally diagnosed as urethral caruncle and was excised under local anaesthesia. The histopathology came as a surprise to us as it revealed diffuse infilteration of large pleomorphic, epitheloid and spindle-shaped tumour cells with high nucleocytoplasmic ratio, vesicular chromatin, prominent nucleoli and scant amount of cytoplasm (figure 2). Melanin pigment was also seen within the cells. Further analysis with immunohistochemistry revealed positive immunostaining with HMB-45 and confirmed it to be primary malignant melanoma of urethra (figure 3). Further workup...

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