Characterization of cell lines from four undifferentiated human malignancies.

Tumor tissue from 4 patients with undifferentiated malignancy was studied by means of electron microscopy and cell culture. The cell lines were characterized for morphologic and ultramorphologic appearance, chromosome constitution, and cell products. Cell types established in culture were compared to histologic diagnosis of the original tumor. In only 1 case originally diagnosed as malignant melanoma were cell cultures and ultrastructure consistent with that diagnosis. Two cases in which cell cultures and ultramorphologic appearance were consistent with melanoma were originally diagnosed as carcinoma and sarcoma. The tumor of the fourth patient, diagnosed as melanoma, had no features in the cell cultures and electron micrographs consistent with melanoma. The reliability of using the presence or absence of melanosomes alone as an absolute diagnostic criterion is doubtful.