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.