Alterations of the clinically noninvolved skin in patients with malignant melanoma. An electron microscopic study before and after repeated application of BCG.

Clinically noninvolved skin of 5 patients with metastasizing malignant melanoma (MM) has been investigated under the electron microscope before and 4 weeks after repeated BCG inoculations (4 X). Increased melanin content, giant and unusual melanosomes, signs of cellular activity and some degenerative changes of the melanocytes were observed both in nontreated and in treated patients. Langerhans cells were markedly stimulated containing melanosome complexes and membrane-bound inclusions of different size and shape. Presence of amyloid, macrophage and plasma cells were also observed prior to and after repeated BCG inoculation, however, cellular infiltration was increased after this treatment and several dermal Langerhans cells appeared. These observations suggest that alterations of the melanocytes occur in MM, which are not confined to the tumor area. Moreover, BCG treatment seems to stimulate the tissue reaction against the tumor, including the activity of Langerhans cells.