A flow cytometric DNA analysis of medullary thyroid carcinoma.

Flow cytometric DNA analysis of biopsy specimens from 10 patients with medullary carcinoma of the thyroid (MCT) was performed to evaluate the possible value of such data as indicators of the biologic behavior of these tumors. Some of the tumors had a unimodal distribution of nuclear DNA content, whereas others were bimodal. The mean modal DNA content in the cells of unimodal medullary carcinomas was not higher than that in the cells of thyroid parenchyma with a normal histologic appearance. This finding contradicts previous reports based on conventional cytophotometry. Bimodal DNA histograms were found in biopsy specimens from four patients, and the two patients with predominantly spindle-shaped cells belonged to this group. The total of nine biopsy specimens with bimodal DNA distributions were all from metastatic foci. Bimodal patterns were found, however, to co-exist with unimodal patterns, when several samples were examined from the same case. Bimodality or more severe aneuploidy did not seem to be related to shorter survival of the patients. The mean value of the percentage of cells in S-phase in our MCT series was higher than in follicular but lower than in anaplastic carcinomas. This fits well with clinical studies, where medullary carcinoma patients have been found to live longer than patients with follicular carcinomas but for a shorter time than those having anaplastic carcinomas.