Nuclear DNA measurements in follicular thyroid adenomas.

The nuclear DNA content was measured retrospectively in histologically confirmed follicular adenomas in 20 patients, and prospectively in 25 patients. In the retrospective group two of the adenomas, and in the prospective group three of the adenomas were classified as atypical due to high cellularity and nuclear atypia, but with no sign of micro-invasive growth. In the group of patients studied retrospectively, the two patients with atypical adenoma had an aneuploid DNA pattern. One of these died 11 years after diagnosis with generalized disease. The other patient in this group with an aneuploid atypical adenoma is alive, as are all the remaining 18 patients with diploid adenomas. In the prospective group there were five aneuploid tumours. The atypical adenomas were aneuploid in two cases and polyploid in one case. No patient in the prospective group has shown any evidence of recurrence so far. Although DNA measurements are of value in distinguishing between low and high malignant potential in invasive tumors, the prognostic information if no invasion is found is uncertain. The importance of examining an adequate number of tissue blocks from the capsular region is emphasized.