Radioiodine breast uptake in nonbreastfeeding women: clinical and scintigraphic characteristics.

UNLABELLED: We studied the scintigraphic and associated clinical characteristics of radioiodine breast uptake in nonbreastfeeding thyroid cancer patients undergoing routine whole-body radioiodine scanning.
METHODS: We performed a retrospective review of the radioiodine scans and medical records of 30 prospectively collected cases.
RESULTS: Twenty-three nonpregnant patients had discontinued breastfeeding for a mean of 11.4 mo. Three postmenopausal and four single nulliparous patients had radioiodine breast uptake on one or more occasions. This represented about 6% of all female patients who had radioiodine scans over a 3-yr period. Four patterns of uptake, full, focal, crescentic and irregular, were observed. Breast uptake mimicked lung metastasis in nine patients. Expressible galactorrhea and moderately elevated prolactin levels were present in 48% and 24%, respectively, of patients examined. In 14 patients followed for an average of 11.4 mo, there were no consistent changes in the pattern or intensity of breast uptake. In 18 patients who had both 123I diagnostic and 131I postablation scans within a few days, breast uptake was present on both scans in 75%. In four patients, breast uptake was present, despite the 4%-9% radioiodine uptake by the thyroid; in one patient, iodinated contrast material blocked the uptake of the thyroid gland but not of the breast.
CONCLUSION: Although the mechanisms of radioiodine breast uptake remain unclear, breast uptake should be suspected in all female patients with radioiodine uptake in the chest area, even in the absence of a history of breastfeeding.