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

Abstract

Melanosis refers to abnormal or excessive deposition of melanin pigment in the cells and/or tissue, which can be seen in any organ but commonly in skin and oral mucosa. Melanosis of the urinary bladder is an extremely rare benign condition and only a handful of cases been reported in the English literature before. In this article, we report a new case of urinary melanosis, describe the differential diagnostic features from pseudomelanosis and offer clues for correct diagnosis. We also provide comprehensive review of the literature on the subject.

Figure 1

Light brown powdery pigments to dark brown globules are mainly present in the cytoplasm, and partially or completely obscuring the nuclei. There are no pigment deposits in the lamina propria.

Figure 2

The pigments stain black by Fontana Mason stain, consistent with melanin.