Primary bladder cancer is most frequently caused by urothelial carcinoma (UC). Other causes of bladder cancer include malignant melanoma, of which a secondary metastasis is far more likely than a primary lesion. Primary melanoma of the bladder is extremely rare, accounting for less than 0.2% of all reported melanoma cases. There is limited literature exploring possible treatment modalities of this rare disease and consequently no standard treatment has been established.

A 75 year old male was found to have an incidental finding of a 2cm anterior bladder lesion identified on routine non-contrast computed tomography (CT) abdomen/pelvis during workup for potential renal transplant. Upon further questioning, it was elicited that he had experienced macroscopic haematuria for four months prior. He subsequently underwent transurethral resection of bladder tumor (TURBT) of a single solid polypoidal mass at the bladder dome. Histopathology was initially reported as an infiltrating papillary UC with no invasion into the muscularis propria (pT1). Re-TURBT confirmed this diagnosis and he received six weeks of intravesical Bacillus Calmette-Guerin (BCG) immunotherapy. Following completion of BCG, repeat rigid cystoscopy identified multifocal disease recurrence involving the entire right lateral wall and bladder neck. This tumour was resected down to the base. Histopathology demonstrated malignant melanoma. Retrospective analysis of the initial resection specimen was consistent with malignant melanoma.

Fluorodeoxyglucose positron emission tomography (FDG-PET) revealed intense FDG uptake over the corresponding region of the bladder wall, without evidence of metastasis or an underlying primary lesion elsewhere. He has since been referred to the medical oncology unit. We subsequently performed a literature review of primary malignant melanoma of the bladder and identified 31 cases. Of these, there are no available texts in the English language describing a patient receiving initial intravesical BCG treatment. Clinical presentation, disease characteristics, treatment options and treatment response were extremely heterogeneous. Treatment included TURBT, partial cystectomy, radical cystectomy, and chemotherapy, both for patients with and without distant metastasis. Survival was varied, and as such no gold standard treatment is apparent.

We demonstrated a rare case of primary malignant melanoma of the bladder that was initially misidentified as UC and therefore treated with intravesical BCG. BCG does not appear to be an effective treatment modality, although no gold standard treatment exists. In patients with disease recurrence or growth despite initial BCG treatment for presumed bladder UC, consideration of other less likely pathologies may be necessary.