Papillary thyroid microcarcinoma: clinicopathological characteristics and implications for treatment in 276 patients

There is debate concerning the clinical significance of papillary thyroid microcarcinoma (PTMC), and therefore, the rise in the incidence of PTMC creates management dilemmas. The purpose of this study was to analyse the clinicopathological characteristics of PTMC in an island region that has a high prevalence of goitre and to determine risk factors for the worst prognosis.

Data from 1874 patients who underwent a total thyroidectomy between January 2002 and December 2008 were reviewed retrospectively. A total of 276 patients who were diagnosed with PTMC in a final pathology report were included in the study. A PTMC was defined as a papillary thyroid carcinoma with a diameter ≤ 10 mm. Clinicopathological features were evaluated by both univariate and multivariate analyses.

Of the 276 patients with PTMC, 219 patients (79·3%) were incidentally diagnosed. Two hundred and two patients had carcinomas of ≤ 5 mm, and 74 patients presented with carcinomas that ranged in size from 0·6 to 1·0 cm. Lymph node metastasis was diagnosed in 3·5% of patients with tumours ≤ 5 mm, and 21·6% of patients presented tumours > 5 mm. Upon multivariate analysis, clinically suspected diagnosis, a tumour size > 5 mm and an age over 45 years at diagnosis were independent risk factors for capsule invasion, while tumour multifocality, bilaterality, size of tumour > 5 mm and thyroid capsule invasion were independent risk factors for lymph node metastasis at diagnosis.

Patients presenting multifocal, bilateral PTMC with a maximum diameter > 5 mm and thyroid capsule invasion may have an increased risk of lymph node metastasis. These factors should be considered in the follow-up for these patients.