Immunohistochemical reactivity of the antimelanoma monoclonal antibody MEL-1

The immunohistochemical reactivity of the monoclonal antimelanoma antibody MEL-1 was evaluated on frozen sections of 9 malignant melanomas, 5 nevi, 1 squamous cell carcinoma, 1 basal cell carcinoma, 2 benign dermal fibrous histiocytomas, 1 infiltrating ductal and 2 infiltrating lobular carcinomas of the breast, 1 primary squamous cell carcinoma and 1 adenocarcinoma of the lung, 1 lung metastasis of gastric adenocarcinoma, 1 adenocarcinoma of the large bowel, 1 lymph node, 1 case of malignant histiocytosis and one of lymph nodal immunoblastic lymphoma, and 1 biopsy of oral cavity mucosa. In primary and metastatic malignant melanoma, junctional nevi, and the upper half of compound and dermal nevi, the staining was intense. Also, benign dermal fibrous histiocytoma and the case of lymph nodal malignant histiocytosis showed an intense reactivity, whereas the immunostaining positivity of the squamous cell carcinoma of the skin, the lung adenocarcinoma, the squamous cutaneous and mucosal epithelium, and the sweat and sebaceous glands was slight. In ductal and lobular infiltrating carcinoma of the breast only focal areas or isolated tumor cells were positive. The lack of reactivity of deep dermal melanocytes of compound and dermal nevi may be correlated with a different antigenic phenotype of the melanocytes. After discussion of the technical problems, the application of MEL-1 was suggested, for diagnostic purpose, to identify lymph nodal metastases in cases of primary self regressed malignant melanoma and to detect lymph nodal metastatic microfoci of malignant melanoma.