NONINVASIVE FOLLICULAR THYROID NEOPLASM WITH PAPILLARY-LIKE NUCLEAR FEATURES (NIFTP): A NEW TERM SINCE 2018. ANALYSIS OF OUR RESULTS.

AUTHORS:
C. Sánchez García (Madrid, Spain) , J. Bernal Tirapo (Madrid, Spain) , F.J. Guadarrama González (Madrid, Spain) , A. Moreno Barguerias (Madrid, Spain) , D. Pastor Altaba (Madrid, Spain) , A. Martínez Pozuelo (Madrid, Spain) , P. Yuste García (Madrid, Spain) , E. Ferrero Herrero (Madrid, Spain)
Background:
The encapsulated non-invasive follicular variant of papillary thyroid carcinoma had an indolent clinical course and a RAS-like molecular profile similar to follicular adenoma.
Methods:
A retrospective analysis of all definitive anatomopathological reports of NIFTP since its introduction in the 4th WHO classification of endocrine tumors of 2017, was performed. A total of 21 cases were found in our center by the Anatomical Pathology Department between 2018 and 2022.
Results:
The preoperative surgical indication was: 6 multinodular goiters, 1 Bethesda III, 6 Bethesda IV (one of them associated with Graves-Basedow disease), 1 Bethesda V and 5 Bethesda VI. In 16 cases a total thyroidectomy was performed, in 4 cases a hemithyroidectomy and one totalization for benign pathology. NIFTP was associated with papillary carcinoma in the same surgical specimen in 7 cases. BRAF mutation study was performed in 10 cases, of which 4 were positive. Among the positive cases, 3 were papillary microcarcinomas (2 presented multifocality) and 1 was a papillary carcinoma with tracheal invasion. Despite the short follow-up time we found no locoregional recurrences.
Conclusions:
In an attempt to decrease overdiagnosis and overtreatment of thyroid cancer, this new definition is not without controversy. Several studies determine that the risk of lymph node metastases is low but not zero. Multicenter studies are needed to answer controversies and to establish follow-up protocols.