Incidental Findings of Thyroid Detected by PET-CT during Cancer Follow-up

Purpose: The incidence of thyroid cancer is increasing in Korea, partially owing to the development of diagnostic tools. Positron emission tomography (PET)-computed tomography (CT), in particular, has generally been used for evaluation of metastasis and follow-up of malignancy. Methods: We retrospectively investigated 2,833 patients with PET-CT for metastasis work-up or cancer follow-up, which was performed between January 1998 and May 2008 at Inha University Hospital. Of them, abnormal thyroid findings were discovered in 181 patients and we studied the result of further evaluation or follow-up PET-CT. Results: Thyroid cancer was diagnosed in 26 patients, including metastatic cancer in 3 patients, and non-operated primary cancer in 2 patients. Other 21 patients received operation, which in all histopathologically revealed papillary carcinoma. The mean age of the 21 patients was 55.4 years. Nine patients had a history of radiotherapy. The site of malignant nodule was discordant between PET-CT and histopathologic result in 6 patients. The mean size of malignant nodules was 9.45 mm (0.1∼23 mm) with microcarcinoma in 10 patients (47.6%). The mean interval between diagnoses was 15.8 months, and in 4 patients operations for two malignancies were performed in a same day. The incidence of thyroid cancer was significantly high in female patients, but the differences of incidence among different cancer groups were not significant for female patients. Conclusion: Early diagnosis of synchronous or secondary thyroid cancer by PET-CT in cancer patients can make early treatment and better strategies for multiple malignancies possible. (Korean J Endocrine Surg 2010;10:249-255)