US AND CT FINDINGS OF SECONDARY NEOPLASMS OF THE THYROID - A PICTORIAL ESSAY

Although clinical series report a low (3%) incidence of metastases to the thyroid gland, autoptic studies have showed occurrences as high as 17%, probably because of the high vascularization of the thyroid. We selected 9 patients who had pathologically proven thyroid metastases a t CT and US, during follow-up for a known primary neoplasm. The most c ommon originating neoplastic primaries include mostly those that gener ally give rise to blood-borne metastases such as breast and lung cance rs, mucoid adenocarcinoma of the stomach; colon cancer and renal cance r, as well as melanoma and leiomyosarcoma. Because of its diffusion, s ensitivity, and noninvasiveness, ultrasonography can justifiably be in troduced in the staging protocols of those neoplasm that more frequent ly give blood-borne metastases to the thyroid, but a US-guided biopsy is warranted for hypoechoic or otherwise suspicious nodules. This hold s particularly true in disease;free patients or previously diagnosed w ith generally slow-growing malignancies (breast or kidney), since the secondary localization, often metachronous in our experience, may be e ffectively managed surgically. CT features, on the other hand, are ext remely variable and are directly dependent on the histology of the pri mary lesion, as well as the size of the secondary lesions. (C) Elsevie r Science Inc., 1998.