A unique case of urinary bladder simple melanosis: a case report and review of the literature

Melanosis refers to abnormal/excessive deposits of melanin in the cells and/or tissue. This condition can be seen in any organ but more frequently in the skin and oral mucosa. Melanosis of the urinary bladder is a very rare benign condition and only 6 cases have been reported in English literature thus far [1-4]. Here, we report a new case, review the previously reported cases and discuss the criteria for making correct diagnosis.The patient is a 77 year-old African-American woman with medical history of urinary incontinence, large volume leakage, and severe urgency with leakage. She has been using diapers for the past two years. She was on Detrol LA for six months but no improvement of her symptoms. The patient was referred to our institution for further treatment. Under cystoscopy examination, clusters of punctuate dark spots were observed on the right lateral aspect of the bladder floor. There were no other lesions identified. Biopsies were obtained from the dark spots, and urine was sent for cytology. The patient had no previous cystoscopy examination or any other pigmented lesions on the skin or mucosal surfaces.The biopsy specimen consisted of multiple tan soft tissue bits ranging from 0.1 to 0.4 cm in greatest dimension. Microscopically, the sections showed benign urothelial mucosa with brown pigments focally present in the cytoplasm of urothelial cells. The pigments ranged from relatively light brown powdery to dark brown globules. The pigments were seen mainly in the cytoplasm and were partially or completely obscuring the nuclei. The underlying lamina propria showed mild congestion and acute inflammation with no pigment deposit (Figure 1). Special stains including Fontana Masson, Periodic Acid Schiff (PAS) and Gomori's iron stain were performed. The pigments were found to be positive by Fontana stain, consistent with melanin (Figure 2), while the stains for PAS and Gomori's iron were negative. The pigments disappeared after bleach procedure, further confir