The diagnostic value of flow cytometric DNA measurements in follicular tumors of the thyroid gland.

Flow cytometric analysis of DNA content was performed on single or multiple samples from 34 thyroidectomy specimens. There were 29 thyroids with diploid DNA content, comprising 15 nonneoplastic lesions, 5 follicular adenomas, 1 medullary carcinoma, and 8 papillary carcinomas. Aneuploid DNA pattern was observed in five cases, including one metastatic mammary carcinoma. The initial histologic diagnoses in the remaining four aneuploid thyroid lesions were follicular carcinoma in one and follicular adenoma in three. The abnormal DNA pattern in the three follicular "adenomas" prompted a review of their aspiration cytologic and histologic features. The fine-needle aspiration biopsy was performed in two of the three cases and showed evidence of a follicular neoplasm with significant nuclear atypia in both. Histologic review of the three lesions led to a modified diagnosis of noninvasive low grade follicular carcinoma in all three. Flow cytometric analysis of DNA content may prove to be a highly useful adjunct in the evaluation of follicular thyroid tumors. Long-term clinical follow-up is warranted to document the clinical significance of these observations.