Preoperative clinicopathological characteristics of patients with solitary encapsulated follicular variants of papillary thyroid carcinomas.

Abstract

Clinical outcomes in patients with the follicular variant of papillary thyroid carcinoma (FVPTC) tend to vary according to the pathological subtypes. We aimed to evaluate the clinicopathological characteristics including preoperative radiological and cytopathological diagnoses in patients with solitary encapsulated FVPTCs (EFVPTCs) to prove the preoperative assessment dilemma. Patients with solitary FVPTCs who underwent thyroid surgery were included. Of 271 patients, 194 patients (72%) had EFVPTCs, whereas 77 patients (28%) had infiltrative FVPTCs (IFVPTCs). EFVPTCs had larger tumor sizes (P < 0.001) and lower frequencies of extrathyroidal extension (P < 0.001) and cervical lymph node (LN) metastasis (P < 0.001) than IFVPTCs. There were significant differences in ultrasonography (US) findings, preoperative cytopathological diagnosis, and the prevalence of BRAF mutations between EFVPTCs and IFVPTCs. Invasive EFVPTCs were diagnosed in 89 patients (33%) and non-invasive EFVPTCs in 105 patients (39%). Non-invasive subtype had smaller tumor sizes (P = 0.001) and lower frequencies of vascular invasion (P = 0.04) and cervical LN metastasis (P = 0.02). There were no significant differences in preoperative US findings and cytopathological diagnoses between invasive and non-invasive EFVPTCs. Clinicopathological characteristics of EFVPTCs, including preoperative US findings, are different from those of IFVPTCs. However, preoperative radiological and cytopathological findings could not distinguish non-invasive and invasive EFVPTCs.