Tumor-associated alpha-2-macroglobulin in human melanomas.

We and others have previously shown that human melanoma cell lines in culture synthesize alpha-2-macroglobulin (alpha 2M). We have now studied melanomas from 30 patients for the presence of alpha 2M using the peroxidase anti-peroxidase technique on histologic sections from paraffin-embedded tissues and primary antibody raised against tumor-associated alpha 2M in rabbits. alpha 2M was detected in 10 of the 30 melanomas studied. In all but 2 cases the presence of alpha 2M was restricted to solitary tumor cells or to solitary foci of tumor tissue. In one case of melanoma almost all tumor cells were positive for alpha 2M, while in the others between 20% and 50% of tumor cells were positive. In all but one of the melanomas, the positivity was characteristic of epithelioid or large-cell type or was confined to this component in melanomas with more than one cell type. In 4 positive cases, differences in the extent of alpha 2M-containing tumor tissue were observed between primary tumor and metastases or metastases from different localizations, with equivocal trend. Clinical follow-up of the melanoma patients suggested that alpha 2M-positively tends to correlate with an unfavorable prognosis.