Papillary microcarcinoma of the thyroid: clinical characteristics and BRAF(V600E) mutational status of 977 cases.

Background: Papillary thyroid carcinoma (PTC) is one of the most common endocrine malignancies. It is estimated that papillary thyroid microcarcinoma (PTMC) accounts for up to 30 % of all PTCs. The clinical significance of PTMC is still unclear, although it may be related to recurrence, distant metastasis, and mortality. The purpose of this study was to analyze the clinical characteristics and BRAF(V600E) mutational status of PTMCs in a Chinese population and to determine risk factors for poor prognosis.

Methods: We performed a retrospective review of 977 PTMC cases that underwent surgical resection from January 2001 to January 2010 at Tianjin Medical University Cancer Institute and Hospital.

Results: The mean size of 977 PTMCs was 5.2 (range, 2-10) mm. Multifocal tumors were seen in 323 patients. The majority of patients (692) had a T1 lesion, whereas 279 had T3 and 6 had T4a; 40.1 % patients had BRAF(V600E) mutation. The frequencies of extrathyroidal extension and lymph node metastasis were 29.2 and 23.4 %, respectively. Distant metastasis was present in 15 patients. Half of the patients (50.8 %) received a total thyroidectomy and others had a lobectomy.

Conclusions: The present study suggests that highly aggressive PTMCs may arise in a subset of patients with BRAF(V600E) mutation and tumors greater than 5 mm. Extrathyroidal invasion, lymph node metastases, and the type of surgical procedures were significantly associated with tumor recurrence. Although multivariate analysis showed that tumor recurrence was not associated with BRAF(V600E) mutation, it has not been shown that treating these patients more aggressively changes outcomes.