Diffuse melanosis in metastatic malignant melanoma.

The skin of a patient with diffuse melanosis as a result of malignant melanoma was examined by light microscopy, immunohistochemistry, and electron microscopy. Our findings indicate that the slate-blue discoloration in this patient was due to pigment deposition in dermal macrophages and endothelial cells. Multiple attempts to identify disseminated metastatic melanoma cells were unsuccessful.