Thyroid Research Thyroid Research Archive Thyroid Cancer

Thirty percent of patients with a thyroid nodule that is a follicular tumor on biopsy prove to have thyroid carcinoma

(March 2002)

The background of the study. Approximately 10 to 20 percent of thyroid nodules that are biopsied are designated follicular tumors or neoplasms. Most of these nodules are benign, but some are malignant. Distinguishing among them requires excision of the nodule and examination of histologic sections looking for invasion of blood vessels and the capsule by tumor cells. This study was done to determine what specific pathologic entities constitute follicular tumors.

How the study was done. During the three-year period January 1998 to December 2000, 1024 nodules were biopsied, of which 184 (18 percent) were follicular tumors (150 patients had a single nodule and 17 patients had two nodules). The nodules ranged in size from 1.0 to 6.0 cm, as determined by ultrasonography.

The results of the study. Among the 167 patients, 139 (83 percent) were women and 28 (17 percent) were men. Among the 122 patients who had surgery (73 percent), 85 had benign nodules (70 percent) and 37 had malignant nodules (30 percent). Among the benign nodules, 51 were hyperplastic nodules, 28 were follicular adenomas, and 6 were lymphocytic thyroiditis. Among the malignant nodules, 25 were papillary thyroid carcinomas (follicular variant), 11 were follicular carcinomas, and 1 was a medullary carcinoma.

The nodule was a carcinoma more often in men (47 percent) than in women (29 percent), in patients ≥40 years old (20 percent) than in those <40 years old (10 percent), and when the nodule was ≥3 cm (55 percent) than when it was <3 cm (23 percent).

The conclusions of the study. A substantial proportion of thyroid nodules with cytologic characteristics of follicular tumors are thyroid carcinomas.

The original article. Baloch ZW, Fleisher S, LiVolsi VA, Gupta PK. Diagnosis of "follicular neoplasm": a gray zone in thyroid fine-needle aspiration cytology. Diagn Cytopathol 2002;26:41-4.