Melanuria

The urinary cytologic findings in a patient with metastatic malignant melanoma, diffuse melanosis and melanuria are presented. The melanosis was diagnosed from the clinical appearance of a generalized slate-blue skin discoloration, which is probably caused by dermal deposition of excess melanin pigment. The melanuria was characterized microscopically by the presence of amorphous, dark-brown casts, which stained positively for melanin pigment, and numerous pigment-laden macrophages.