Context: The chance that a thyroid nodule is malignant is higher when there is a history of childhood radiation exposure.
Objective: The objective of the study was to determine how the size of a thyroid nodule, the number of nodules, and the distribution of nodules influence the risk of cancer in irradiated patients.
Patients: From a cohort of 4296 radiation-exposed people, we studied the 1059 that underwent thyroid surgery. DESIGN AND OUTCOMES: We studied the association between the size, number, distribution, and rank order of thyroid nodules and the chance of malignancy.
Results: There were 612 malignant nodules in 358 patients and 2037 benign ones in 930 patients. There was no change in the risk that a nodule was malignant with increasing size (odds ratio 0.91/cm, P = 0.11) among the 1709 nodules that were 0.5 cm or greater. A solitary nodule had a similar likelihood of being malignant as a nodule that was one of several (18.8 vs. 17.3%), whereas patients with multiple nodules were more likely to have thyroid cancer than those with solitary nodules [30.7 vs. 18.7%; risk ratio 1.64 (1.27-2.13)]. Aspirating only the largest nodule would have missed 111 of the cancers (42%), whereas aspirating the two largest nodules would have missed 45 of the cases (17%), although none would have been 10 mm or greater.
Conclusions: In radiation-exposed patients, the following conclusions were made: 1) the likelihood that a nodule is malignant is independent of nodule number and size; 2) the likelihood of cancer is increased if more than one nodule is present; 3) evaluating the two largest nodules by fine-needle aspiration would have resulted in a significant number of cases being missed but none with large cancers; and 4) more than half of the patients with thyroid cancer had multifocal tumors.