NIFTP | Acta Medica Marisiensis

Objective: In 2016 a group of expert endocrine pathologists proposed a new terminology, NIFTP (Non-invasive follicular thyroid neoplasm with papillary-like nuclear features) for a histological subtype of thyroid carcinoma (encapsulated follicular variant of papillary thyroid carcinoma, non-invasive type). In this study, we aimed to assess on a retrospective basis the epidemiological trend and overall incidence of NIFTP in Mureș county, Romania, over a six-year period (2016-2021).
Methods: All NIFTPs registered between 2016-2021 in Târgu-Mureş Pathology Departments were reevaluated. NIFTP’s incidence was calculated by dividing the number of NIFTPs with the number of papillary thyroid carcinomas (PTCs). Further on, we compared NIFTP’s incidence between 2016-2018 with NIFTP’s incidence between 2019-2021, as the diagnostic criteria of NIFTP were revised in 2018.
Results: Forty-six cases of NIFTP were registered in our departments between 2016-2021, resulting in an overall NIFTP incidence of 17.9 % [CI (95%): 7.6-32.5] among the 257 PTCs. When we compared the NIFTP’ incidence between the two study periods (2016-2018 versus 2019-2021), our data revealed that the NIFTP’s overall incidence has dropped from 21.4 % [CI (95%): -14.5-60.1] to 15% [CI (95%): -8.2-43] in the second evaluated period (p=0.034).
Conclusion: The overall NIFTP incidence was low in our departments between 2016-2021. Moreover, NIFTP’s incidence decreased after 2018, following revision of the diagnostic criteria. Our results highlight that very stringent morphologic criteria need to be apply when making a diagnosis of NIFTP, in order to avoid a misdiagnosis and/or an overtreatment of a tumor with indolent behavior.

Histopathological Diagnostic Criteria for Non-invasive Follicular Thyroid Neoplasm with Papillary-like Nuclear Features Highlighted by Six Illustrative Cases

Adela Nechifor-Boilă^1,2, Edit Dee², Angela Borda^1,3

1. Department of Histology, University of Medicine and Pharmacy of Tîrgu-Mureș, Romania
2. Department of Pathology, Tîrgu-Mureș County Hospital, Romania
3. Department of Pathology, Tîrgu-Mureș Emergency County Hospital, Romania

DOI: 10.2478/amma-2018-0015

Introduction. The encapsulated, non-invasive subtype of follicular variant of papillary thyroid carcinoma (FVPTC) represents approximately 10% to 20% of all thyroid cancers. Many studies over the past decade have shown that these tumors carry an indolent clinical course, with no recurrence, even in patients treated by lobectomy. Their reclassification as neoplasms with “very low malignant potential” has recently been suggested by an international group of experts and a new terminology was proposed: “non-invasive follicular thyroid neoplasm with papillary-like nuclear features” (NIFTP). However, a diagnosis of NIFTP is still challenging for many pathologists in daily practice.
Presentation of case series. By presenting six illustrative cases of NIFTP, this article aims to highlight the diagnostic criteria and the burden difficulties when dealing with NIFTP cases. Characteristic histological features, inclusion and exclusion criteria for NIFTP, as well as sampling guidelines and differential diagnosis challenges are all discussed.
Conclusions. The diagnosis of NIFTP is not straightforward and requires meeting strict inclusion and exclusion criteria. Total sampling of the tumor capsule in these cases is mandatory in order to exclude invasion (capsular and/or vascular). A diagnosis of NIFTP promotes a less-aggressive patient management that is, no need for completion thyroidectomy or radioactive iodine therapy.