A Comparative Study on BRAFV600E Mutation, Sonographic Findings, and Pathologic Characteristics in Non-invasive Follicular Thyroid Neoplasm with Papillary-like Nuclear Features (NIFTP) and Invasive Follicular Variant of Papillary Thyroid Carcinoma (IFVPTC)

Objective: Noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) comprise a new subgroup of thyroid tumors of follicular origin with borderline histologic features that lack evidence of either capsular or vascular invasion. In contrast to the invasive follicular variant of papillary thyroid carcinoma (IFVPTC), adverse events such as cancer-related death, distant or regional metastases, and structural or biochemical recurrence do not occur in patients with NIFTP. Many studies have been done to elucidate these two specific types of papillary thyroid cancer (PTC) and reduce aggressive therapeutic actions. This study compares molecular, cytological, and radiologic features of NIFTP and IFVPTC. Methods & Materials: Two groups of patients with NIFTP and IFVPTC (n = 18 in each group) who were referred to the endocrine clinic, at Imam Reza Hospital, were enrolled in this cross-sectional study. Molecular analysis for BRAFV600E mutation of thyroid tissue was evaluated for all cases. Patient data included: age, sex, type of surgery, thyroid sonographic findings, and prior cytological diagnosis with the Bethesda system for reporting thyroid cytopathology. Results: Only two cases in the IFVPTC group were positive for BRAFV600E mutation. The majority of NIFTP cases were diagnosed as benign lesions (8/18). In contrast, the majority of IFVPTC cases were diagnosed as suspicious for malignancy on cytology (7/18). The mean nodule size in ultrasound in the NIFTP group (41.81 ± 20.43 mm) was larger than the IFVPTC group (36.72 ± 20.73 mm) (p =0.47). Most cases in the IFVPTC group had significantly multiple nodules (72.2%), while most cases in the NIFTP group (81.3%) had solitary nodules. Nodule composition in both groups was solid and complex; however, no cystic nodules were detected in ultrasound examinations. Furthermore, no calcification or lymphadenopathy was seen in the majority of cases in ultrasound. In the IFVPTC group, 47.1% and 35.3% of nodules were hyperechoic and hypoechoic, respectively, while 23.1%, 38.5%, and 23.1% of nodules in the NIFTP group were heterogenic, hyperechoic, and hypoechoic, respectively. Conclusion: According to our findings, only 11.1% of IFVPTC cases were BRAFV600E-positive, while none of the patients in the NIFTP group showed this mutation. However, IFVPTC was predominantly associated with a preceding diagnosis of PTC on FNA, and NIFTP was associated with the preceding diagnosis of benign lesions and follicular neoplasm. Sonographic findings failed to distinguish NIFTP from IFVPTC.