Primary malignant melanoma of the female urethra: A case report

Abstract

Primary malignant mucosal melanoma of the female urethra is extremely rare and associated with high recurrence rates and exceptionally poor 5-year survival. Due to its rarity, treatment strategies are heterogenous and often extrapolated from the treatment of other more common types of melanomas. Herein, we describe a case of malignant melanoma of the urethra in a Caucasian female.

1 Introduction

Primary mucosal melanoma (MM) of the urethra is a rare malignancy which accounts for 0.2 % of all melanomas. . It arises from melanocytes located within the basal cell layer of the epithelium at different anatomic sites. Melanocytes may or may not produce melanin pigmentation and can give rise to melanomas in many different locations, including respiratory, gastrointestinal and urogenital tracts. . Metastatic spread occurs early in urethral melanomas, through lymphatic and haematogenous spread. These cases usually present with haematuria, obstructive urinary symptoms, protruding mass, pain and/or urethral discharge. .

2 Case presentation

A 78-year-old woman presented to the urology outpatient clinic for a review of a rapidly growing, painful periurethral lesion. She was initially referred to and assessed by the gynaecology team who appreciated a firm mass at the anterior aspect of the vaginal introitus. The mass was reported to extend to the anterior vaginal wall, but the origin appeared to be the posterior aspect of the urethra. Her past medical history consisted of posterior neck basal cell carcinoma (excised), insulin-independent diabetes mellitus, atrial fibrillation and hypertension.

Prior to assessment in the urology clinic, the patient underwent a Computed Tomography (CT) Urogram which did not demonstrate any intra-abdominal lymphadenopathy, urinary tract lesions or an obvious mass at the level of the urethra. However, physical examination confirmed the presence of a 3cm × 1cm solid mass at the distal posterior urethra which was tender to palpitation with no evidence of bleeding. Unfortunately, the urethral meatus was not identified due to the mass causing pain and anatomical distortion and flexible cystoscopy was not performed in the clinic. To further evaluate the nature of this lesion, a Magnetic Resonance Imaging (MRI) of the pelvis was requested. The MRI Pelvis confirmed the presence of a 22mm solid urethral meatus tumour of unknown aetiology ( Fig. 1 ), and a decision was made to excise the lesion and reconstruct the urethra. Under general anaesthetic, the urethral meatus lesion was identified, and a rigid cystoscopy demonstrated an endoscopically normal bladder and proximal urethra.

The lesion was successfully excised in the same manner as excision of urethral caruncle and histology revealed B-RAF negative malignant melanoma ( Fig. 2 a–c) with positive surgical margins. The malignant cells were immunoreactive for Melan-A and SOX 10, which are typical for melanoma. They were negative for cytokeratin, CD45, CD30 and Synaptophysin. In view of this histology, Positron Emission Tomography/CT (PET/CT) was arranged and confirmed FDG uptake at the mid urethra at the excision site (extending over 20mm) ( Fig. 3 ) but nowhere else in the body. As per the melanoma multi-disciplinary meeting (MDM), MRI head was performed showing no evidence of metastases.