Clinical-Pathological and Molecular Evaluation of 451 NIFTP Patients from a Single Referral Center

Background: Non-invasive follicular thyroid neoplasms with papillary-like nuclear features (NIFTPs) were introduced in thyroid pathology in 2016. NIFTPs are a group of follicular neoplasm with an indolent behaviour. In this study, we gathered a large retrospective cohort of NIFTPs and compared those presenting as solitary lesions and NIFTPs found in multifocal setting. Methods: A retrospective search of NIFTPs was performed, and the clinico-pathological features were recorded. For a subgroup of patients, pre-surgical ultrasound (US) evaluation, cytological diagnosis, and molecular analysis were available. Results: We collected 451 NIFTPs; 254 (56.3%) were truly solitary tumours, while 197 coexisted with one or more NIFTP/cancer. Contrasting unifocal and multifocal settings, NIFTPs size was the only significantly different parameter. Preoperatively, NIFTP nodules mostly showed low-risk US characteristics, indeterminate cytology and a RAS-like molecular profile. Conclusion: NIFTPs often coexist with collateral thyroid tumours. However, no clinical-pathological differences can be observed between solitary and multifocal NIFTPs. Despite the well-established clinical indolence of NIFTP, a careful monitoring of the contralateral lobe should not be excluded.

Automated summary

This study retrospectively analyzed a large cohort of NIFTPs and compared the clinico-pathological features of solitary and multifocal lesions. The results showed that NIFTPs often coexisted with other thyroid tumors, but no significant clinical-pathological differences were observed between them. Therefore, careful monitoring of the contralateral lobe is still important.