Comparison of clinicopathological features in patients with noninvasive follicular thyroid neoplasm with papillary-like nuclear features and follicular variant papillary thyroid cancer

Abstract

INTRODUCTION Noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) is a newly defined entity accepted as a tumor precursor. OBJECTIVES We aimed to examine the features of patients diagnosed with follicular variant papillary thyroid carcinoma (FVPTC), which are classified as NIFTP in the recent classification. This study compares clinical, radiological, histopathological, and molecular features of NIFTP and FVPTC. PATIENTS AND METHODS A total of 247 patients with FVPTC were retrospectively examined and pathology specimens were reviewed. RESULTS Patients were divided into 2 groups (NIFTP group: 107 patients; FVPTC group: 140 patients). There was a difference in terms of the percentage of pathologic nodules with irregular borders detected on preoperative neck ultrasonography (NIFTP group: 6.5%, FVPTC group: 15.7%; P = 0.02). Central lymph node dissection specimens of 50 patients in the NIFTP group were normal, while 4 of 70 patients (5.7%) in the FVPTC group had lymph node metastasis (P = 0.14). In addition, multivariable analysis (binary logistic regression) showed that FVPTC was positively associated only with irregular borders and extrathyroidal extensions (P = 0.02 and P <0.001, respectively). CONCLUSIONS We suggest that patients diagnosed with NIFTP according to the new classification are considered low risk, and margin characteristics of the nodule detected on preoperative ultrasonography may be helpful in the differential diagnosis.