Malignant melanoma with renal dense deposits containing tumor antigens.

A patient with disseminated malignant melanoma developed mild renal failure with proteinuria four months following the diagnosis of his neoplasm. Renal biopsy showed a membranoproliferative glomerulonephritis. Electron microscopy revealed intramembranous dense deposits in the glomeruli as well as in tubular basement membranes and Bowman's capsule. Immunofluorescence microscopy demonstrated granular staining for C3 in these same locations and granular deposits of immunoglobulins in the glomerular capillary loops. Light and electron microscopy of the autopsy kidney obtained 5 months later revealed progression of the number, size and density of the deposits. Eluates from both autopsy and biopsy kidney contained melanoma antigen and anti-melanoma antibodies. This case illustrates the association between the dense deposits and neoplasia with the dense deposits representing immune complexes with the tumor as antigen.