Identification of submicroscopic lymph node metastases in patients with malignant melanoma.

In order to detect micrometastatic disease, our laboratory has developed a method for evaluating lymph node sections from patients with stage 1 or 2 melanoma. Lymph nodes isolated from standard dissections are bivalved; one half is subjected to routine histopathological evaluation and the other half disrupted and placed into cell culture. The cultured cells are identified by cytologic examination, immunohistologic staining, and the presence of melanoma-associated antigens. Lymph nodes (448) from 62 patients with malignant melanoma were evaluated by tissue culture. Fifteen patients were upgraded from stage 1 or 2 to stage 3 disease after micrometastases were identified in lymph node cultures. Recurrence of disease in histologically node negative patients, during a mean 24-month follow-up, has only been observed thus far in patients with culture positive lymph nodes. In addition, these results add evidence to the belief that missed micrometastatic disease in regional nodes is a sign of occult systemic metastases that would account for the defined recurrence rate in histologically node negative patients.