Thyroid nodules in the follow-up of irradiated individuals: comparison of thyroid ultrasound with scanning and palpation.

In 1974 we began a prospective study of a cohort of 4296 individuals exposed to therapeutic head and neck irradiation during childhood for benign conditions. To define the role of thyroid ultrasonography in following irradiated individuals, we studied a subgroup of 54 individuals. They all had been screened between 1974-1976 and had normal thyroid scans and no palpable nodules at that time. Thyroid ultrasonography, thyroid scanning, physical examination, and serum thyroglobulin measurements were performed. One or more discrete ultrasound-detected nodules were present in 47 of 54 (87%) subjects. There were a total of 157 nodules, 40 of which were 1.0 cm or larger in largest dimension. These 40 nodules occurred in 28 (52%) of the subjects. Thirty (75%) of these 1.0-cm or larger nodules matched discrete areas of diminished uptake on corresponding thyroid scans. The 10 that did not match (false negative scans for > or = 1.0-cm nodules) were the only nodules of this size in 7 subjects. Of 11 nodules 1.5 cm or larger, only 5 were palpable. Serum thyroglobulin correlated to the number (P = 0.04; r2 = 0.10), but not the volume of the thyroid nodules (P = 0.07; r2 = 0.08). We conclude that thyroid nodules are continuing to occur and are exceedingly common in this irradiated cohort of individuals. The results confirm that thyroid ultrasonography is more sensitive than physical examination and scanning. However, thyroid ultrasound is so sensitive and nodules so prevalent that great caution is needed in interpreting the results.