An investigation into noninvasive follicular thyroid neoplasms with papillary-like nuclear features: does the initial proposal on noninvasive follicular thyroid neoplasms with papillary-like nuclear features behavior hold true?

Current management of patients with noninvasive follicular thyroid neoplasms with papillary-like nuclear features (NIFTP) is lobectomy with close clinical follow-up. Because this entity is still young, we present our 5-year institutional experience with NIFTP since that time. Cases of NIFTP diagnosed from 2017 to 2022 were identified. Data points including patient demographics, radiology, cytologic and pathologic diagnoses, molecular profiles, and clinical follow-up were documented. A literature review of NIFTP case series was performed. A total of 379 cases were included (mean age: 52 years, female:male ratio 3.3:1). Ultrasound findings were available for 260 patients, and 247 underwent fine-needle aspiration (FNA). The FNA diagnoses per the Bethesda System for Reporting Thyroid Cytology were nondiagnostic (n = 2), benign (n = 16), atypia of undetermined significance/follicular lesion of undetermined significance (n = 119), follicular neoplasm/suspicious for follicular neoplasm (n = 68), suspicious for malignancy (n = 31), and malignant (n = 11). Molecular testing was performed in 179 cases. Lobectomy was performed for 183, total thyroidectomy for 192, and nodulectomy for 4 cases. The average size of NIFTP was 2.3 cm, and 232 cases had additional nodules (including benign and malignant neoplasms). Multifocal NIFTP occurred in 32 patients. Lymph nodes were evaluated in 196 cases with metastatic carcinoma in 29 cases (all with concurrent diagnoses of carcinoma). Most patients were alive at follow-up, 100 were lost to follow-up, and three died from other causes. Literature review revealed 2870 NIFTP cases with similar patient demographics and pathologic findings. We confirm that NIFTP is a low-risk neoplasm with indolent clinical behavior, which can be managed conservatively.