Melanocytes in nevi and melanomas synthesize basement membrane and basement membrane-like material. An immunohistochemical and electron microscopic study including immunoelectron microscopy

Light microscopic studies have shown that nevus cell nests and melanoma nes ts are surrounded by basement membrane (BM) material containing type IV col lagen and laminin. This study confirms this by electron microscopy and rela tes it to proteins which interact with the basement membrane. Nevi except f or dysplastic and Spitz nevi, malignant melanomas, and melanoma metastases were studied by immunohistopathology, routine electron microscopy (EM), and immunoelectron microscopy. The lesions were incubated with monoclonal anti body (moAb) against type IV collagen, laminin, and the integrin as and stud ied by light microscopy. In addition, melanomas were studied by immuno-EM a fter incubation with a moAb against matrix metalloproteinase-2 (MMP-2). Nev us cell nests and melanoma nests are surrounded by BM material containing t ype IV collagen and laminin by immuno-EM. The BM material various in thickn ess and is amorphous. Type IV collagen, laminin, and MMP-2 are synthesized by melanoma cells as well as adjacent fibroblasts. Destruction or loss of t he BM is not mandatory for melanoma invasion or even metastasis. Possibly t he BM material is a protective wall for melanoma cells. Interactions betwee n melanocytes and the extracellular matrix of which the BM is a part, can b e traced back to the migration of melanocytes from the neural crest.