The background of the study. Most papillary thyroid carcinomas can be identified by fine-needle aspiration biopsy, but follicular carcinomas and follicular variants of papillary carcinoma cannot be distinguished from benign nodules. This study was undertaken to determine if benign thyroid nodules could be distinguished from thyroid carcinomas by gene profiling.
How the study was done. Abnormal thyroid tissue was obtained at surgery from 59 patients (50 women, 9 men; mean age, 51 years) with a thyroid nodule. The nodule was a follicular adenoma or hyperplastic nodule in 26 patients, a papillary carcinoma in 11, a follicular variant of papillary carcinoma in 13, and a follicular carcinoma in 11.
RNA was extracted from the tumors, amplified, and hybridized to 627 genes on a gene chip. After staining, the chips were scanned to detect hybridization signals. The results were analyzed by cluster analysis, which led to grouping of genes according to whether they were more than two times underexpressed or overexpressed.
The results of the study. As a test set, 21 benign nodules and 24 papillary (including follicular variants) and follicular carcinomas were studied. Among the 627 genes, 61 were overexpressed and 72 were underexpressed in the papillary and follicular carcinomas, as compared with the benign nodules. The profile of one follicular adenoma was similar to that of the carcinomas, and the profile of one follicular variant of papillary carcinoma was similar to that of the benign nodules. Addition of the results from five benign nodules and nine carcinomas resulted in two similar, distinct groups; the profile of one follicular adenoma was similar to that of the carcinomas, and the profile of three follicular variants of papillary carcinoma was similar to that of the benign nodules. The sensitivity was 91 percent and the specificity was 96 percent for the detection of carcinoma.
The conclusions of the study. Different genes are activated and inactivated in benign thyroid nodules and papillary and follicular thyroid carcinomas, and the differences can be detected by gene profiling.
The original article. Finley DJ, Zhu B, Barden CB, Fahey TJ III. Discrimination of benign and malignant thyroid nodules by molecular profiling. Ann Surg 2004;240:425-37.