Melanoma of the urinary bladder: a review of the literature

Abstract

Background. Melanomas of the urinary bladder and urethra are rare. Aims. To review the literature on the disease. Methods. Various Internet databases were used to identify reported cases of the disease. Results. Less than 30 cases of primary melanoma of the urinary bladder and urethra have been reported in the literature and they have been associated with melanosis and commonly with metastases. The lesions may be primary or metastatic with no gender preference. The diagnostic features include pigmented raised lesions which histologically exhibit spindled or epitheliod cells, necrosis, mitotic figures, and atypical melanocytes. Immunohistochemically they stain positively with S100; HMB45; and other melanocyte markers, but negatively with Keratin and Vimentin. The treatment involves excision and possibly IL-2. The prognostic factors include size and depth of invasion as well as metastatic lesions. Conclusions. Less than 30 cases (about 24 cases) of the disease have been reported. There are also reports of metastatic melanomas of the urinary bladder emanating from primary melanomas originating elsewhere. Diagnosis of the primary disease is based upon the histological appearance of the lesion, positive staining with S100 and HMB45, and evidence of absence of melanoma elsewhere. Primary melanoma of the bladder is usually a fatal lesion.

Figure 1

Haematoxylin and Eosin staining showing melanosis and not melanoma: this shows light brown powdery pigments to dark brown globules which are mainly present in the cytoplasm, partially or completely obscuring the nuclei. There is no evidence of any pigment deposit in the lamina propria. Taken from Jin et al. [52].

Figure 2

Fontana Masson stain for melanin: standard resolution. The pigments stain brown by Fontana stain which is consistent with melanin. Taken from Jin et al. [52].

Figure 3

Bladder metastatic melanoma. Haematoxylin and Eosin stain: primary melanoma of the urinary bladder is very rare. In comparison, between 15% and 20% of patients who are dying of melanoma have urinary bladder involvement. This figure represents metastasis to the urinary bladder in a patient with known history of malignant melanoma, taken from Bladder Melanoma Pathology http://outlines.com/ with permission to reproduce the figure from info@biomedcentral.com.

Figure 4

Bladder metastatic melanoma immunohistochemistry for HMB45. The differentiation of malignant melanoma from high-grade urothelial carcinoma may not be easy. Immunohistochemical staining for HMB-45 as depicted in the figure may help in the establishment of the correct diagnosis, taken from Bladder Melanoma Pathology http://outlines.com/, with permission to reproduce the figure from the original author source granted by info@biomedcentral.com.