Higher body mass index may be a predictor of extrathyroidal extension in patients with papillary thyroid microcarcinoma

Recently, higher body mass index (BMI) has been associated with aggressive pathologic features of papillary thyroid carcinoma. The aim of this study was to clarify the relationship between BMI and aggressive pathologic features of papillary thyroid microcarcinoma (PTMC) and to evaluate whether the BMI can be a prognostic factor of PTMC. This retrospective study included 612 PTMC patients who underwent surgical excision at a referral center between April 2006 and December 2007. Patients were grouped according to BMI (<25 or ≥25 kg/m²). Multivariable logistic regression analysis was performed to determine independent predictors of aggressive pathologic features (advanced stage, extrathyroidal extension, and lymph node metastasis), with adjustment for age, gender, tumor size, multifocality, thyroid stimulating hormone (TSH) level, and BMI (value/group). PTMC patients with a BMI ≥ 25 kg/m² showed significantly higher prevalences of extrathyroidal extension, advanced pathologic TNM stage, and male gender, compared to those of patients with a BMI < 25 kg/m². Lymph node metastasis and mean TSH level were not significantly different between the two BMI subgroups. In multivariable analysis, the BMI ≥ 25 kg/m² group was positively associated with the presence of extrathyroidal extension (adjusted odds ratio 1.49, P = 0.05). Higher BMI was associated with extrathyroidal extension in PTMC patients. This study suggests that the BMI could be considered as a prognostic factor for predicting the presence of extrathyroidal extension and it may help decide the appropriate surgical extent for PTMC patients.