Diagnosis and therapeutic strategy for papillary thyroid microcarcinoma.

HYPOTHESIS Total thyroidectomy followed by radioactive iodine I 131 treatment is effective in papillary thyroid microcarcinoma (PTM) with lymph node or extrathyroid invasion. DESIGN Retrospective study. SETTING Chang Gung Medical Center, Linkou, Taiwan. PATIENTS A total of 227 patients with PTM, categorized into high-risk (n = 12) and low-risk (n = 215) groups according to age, metastases, extent, and size criteria. INTERVENTIONS Diagnosis and treatment of PTM. MAIN OUTCOME MEASURES Time and method of diagnosis, operative method, metastases, and survival. RESULTS In 51 patients, PTM was identified on preoperative fine-needle aspiration cytology; in 75 patients, diagnosed in frozen sections during operation; and in 101 patients, diagnosed incidentally in the final histopathological examination. Among these 3 groups, 18% (9/51), 17% (13/75), and 78% (79/101), respectively, underwent subtotal thyroidectomy or lobectomy for tumors. Four cases (1.8%) displayed distant metastases at diagnosis. Only 0.9% of patients with PTM (2 of 227) died of thyroid cancer. One hundred eighty-nine cases of PTM were confined to the thyroid, 22 had lymph node metastases, and 16 showed extrathyroid extension, including soft-tissue invasion and distant metastases. Sex, operative methods, follow-up status, and mortality showed differences in these groups. Five of 227 patients remained in non-disease-free status at follow-up. CONCLUSIONS Approximately 10% of PTMs exhibited progressive clinical courses, while less than 1% resulted in mortality. Age, sex, and postoperative thyroglobulin level were the main prognostic factors in the high-risk group of patients with PTM. Conservative treatment of the incidental finding of PTM after suitable postoperative assessment is justified.