Non-invasive follicular thyroid neoplasm with papillary-like nuclear feature: clinical, pathological, and molecular update 5 years after the nomenclature revision.

The term non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) was proposed in 2016 and incorporated as a new entity in the World Health Organization (WHO) classification of tumours of endocrine organs in 2017. Since then, there has been debate regarding the histological criteria for the diagnosis, the need for molecular studies or the risk of lymph node metastasis or recurrence associated with this entity. Over the years, the concept of NIFTP evolved, now including both small (<1 cm) and large (>4 cm) tumours and oncocytic lesions. On the other hand, recent data on NIFTP in the setting of thyroid follicular nodular disease or frequent coexistence of malignant tumours raised concerns regarding the follow-up of these patients. Today, both pathologists and clinicians still face several challenges in the diagnosis, treatment, and follow-up of patients with NIFTP.