Fifty-four tissues of human melanomas from 33 patients with primary or metastatic lesions were cultivated in vitro using several chemically defined media supplemented with horse, calf, or human serum. Forty-two or 77.8 per cent developed outgrowths in vitro.

All cultures exhibited radial outgrowths, and cells migrated as independent units. The dendritic melanocyte resembled a nerve cell in its initial emigration in vitro.

The melanocyte was found in various stages of differentiation ranging from the undifferentiated uni- or bipolar form, in cultures of anaplastic melanomas, to the differentiated dendritic form in cultures of more heavily pigmented melanomas. The dendritic form was observed in most pigmented cultures regardless of primary or metastatic site. Melanin formation in vitro coincided with the aggregation and differentiation of the melanocytes which increased with age of the cultures.

Prior treatment in vivo appeared to influence subsequent successful growth in vitro, as indicated by 95.8 per cent successful tissue culture growth in melanomas from untreated patients and only 70.3 per cent successful growth from patients who had received prior radiation or chemotherapy or both.

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This investigation was supported, in part, by research grants from the National Cancer Institute (C-2780, CY2779) of the National Institutes of Health and, in part, by the Damon Runyon Memorial Fund for Cancer Research, Inc.

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