Size, number, and distribution of thyroid nodules and the risk of malignancy in radiation-exposed patients who underwent surgery.
BACKGROUND
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.


METHODS
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.
Mihailescu
Dan V
DV
Section of Endocrinology, Diabetes, and Metabolism, College of Medicine, University of Illinois at Chicago, 1819 West Polk Street, Chicago, IL 60612, USA.
Schneider
Arthur B
AB
D002277:Carcinoma / Q000453:epidemiology / Q000209:etiology* / Q000473:pathology; D015331:Cohort Studies; D005500:Follow-Up Studies; D006801:Humans; D009381:Neoplasms, Radiation-Induced / Q000453:epidemiology / Q000209:etiology* / Q000473:pathology; D009929:Organ Size; D015995:Prevalence; D012042:Registries; D012189:Retrospective Studies; D012307:Risk Factors; D013964:Thyroid Neoplasms / Q000453:epidemiology / Q000209:etiology* / Q000473:pathology; D016606:Thyroid Nodule / Q000473:pathology* / Q000601:surgery*; D047368:Tumor Burden / Q000502:physiology*