Melanoma. An ultrastructural study of the host inflammatory and vascular responses.

Electron microscopic studies of 4 surgically excised human primary superficial spreading melanomas of the skin were done with special emphasis on the host inflammatory and vascular responses to tumor. Host cells participating in the inflammatory response included numerous small lymphocytes, activated macrophages, and mast cells. Some mast cells had lost local portions of granule content, but complete degranulation of mast cells was not seen. Activated macrophages had avidly ingested melanin granules and cellular debris and often were close to dying tumor cells. Lymphocytes, many displaying motile forms, were actively invading the epidermis; formed perivascular cuffs around damaged vessels; and were in intimate contact with living, damaged, and dead melanoma cells. Basophils, eosinophils, and neutrophils were absent from inflammatory infiltrates. Changes of the microvasculature included focal endothelial necrosis and hypertrophy as well as basal lamina changes indicative of repeated episodes of endothelial injury, necrosis and regeneration. These findings are discussed in relationship to a number of recent studies of the immunologically-mediated inflammatory responses to contact allergy, graft rejection, and syngeneic tumor rejection, in man and animals.