[Diffuse melanosis and melanuria in malignant melanoma]. / Melanosis difusa y melanuria en melanoma maligno.

A new case of diffuse melanosis with melanuria is reported. Light and electron microscopic technics were employed. Several hypothesis were proposed to explain the pathogenesis of this particular pigmentation: Dermal perivascular histiocitic cells phagocyte organelles originated in lysed circulating melanoma cells. Phagocytosis of the altered circulating melanoma cells by the endothelium. Macrophages containing ingested melanin migrate from the capillary lumen into the dermis. We consider that in this particular pigmentation participate two mechanism: a) The perivascular dermal macrophage phagocyte the pigment originated in the lysis of the circulating melanoma cells. b) Macrophages loaded with pigment granules cross the capillary wall and remain around the blood vessels.