Most cases of papillary microcarcinomas of the thyroid (PMC) are not palpable and are clinically asymptomatic. The natural history of the microcarcinoma is unclear and remains debatable. There is continued discussion of whether thyroid microcarcinomas should be treated surgically and to what extent surgical removal should be extended. The main goal of this study was to analyze the clinical features and to determine the appropriate surgical treatment for well differentiated PMC in one lobe of the thyroid with favorable features in regard to consideration of radical surgery.

We studied 134 patients with the histological diagnosis of PMC from March 2003 to January 2006. The tumor was defined as 10 mm or less in the greatest diameter according to the World Health Organization guidelines. For all patients we confirmed the diagnosis by ultrasoundguided fine-needle aspiration biopsy (US-FNAB) preoperatively. There were 11 men and 123 women. The age at initial treatment ranged from 22 to 74 years (mean 46). Thyroid resection was lobectomy in 31 (23.1%) and total thyroidectomy (TT) in 103 (76.9%). CCND was performed routinely at the time of thyroidectomy. Lateral neck dissection was carried out in eight patients (5.9%) who had biopsy-proven metastatic cervical lymphadenopathy demonstrated clinically or by imaging. Patient records were reviewed retrospectively. Categorical variables were analyzed using the chi-square test or Fisher's exact test. Two-sided Student's t-test was used to compare paired data.

The mean tumor size was 6.77 mm. PMC was associated in 36.6% (49/134) with lymph node metastasis, in 20.1% (27/134) with multifocality and in 26.9% (36/134) with capsular invasion. The mean tumor size differences influenced lymph node metastasis (LNM) (P<0.05). Capsular invasion (38.8%, 19/49) and multifocality (30.6%, 15/49) were associated with LNM (P=0.018, 0.022 respectively). The subdivision of primary tumors according to size (<or=5 mm vs. >5 mm) influenced multifocality (P=0.031). The frequency of LNM, in the contralateral central compartment of patients with lesions in one lobe of thyroid, without capsular invasion, underwent TT with CCND in 1.7% (1/59).

Currently, thyroidectomy with lymph node dissection has been the recommended first line treatment for microcarcinoma of the thyroid because of the high incidence of multifocality and lymph node metastasis. However, when we excluded patients with aggressive prognostic features we could successfully perform lobectomy and isthmusectomy with ipsilateral CCND based on considerations of radical surgery (98.3%, 58/59). However, subsequent surgery for contralateral nodes or lobe metastasis would not be easy and a longer follow-up period would be required to confirm our hypothesis with regard to the long term recurrence and mortality.