Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features: Can Cytology Face the Challenge of Diagnosis in the Light of the New Classification?

Abstract

Objectives: To assess the cytological findings of noninvasive follicular thyroid neoplasms with papillary-like nuclear features (NIFTP), conventional papillary thyroid carcinomas (C-PTC), and invasive follicular variants of papillary thyroid carcinomas (IFV-PTC) to determine if there are cytological differences between groups. Study Design: We have reviewed all thyroid fine-needle aspiration cytology samples diagnosed between 2000 and 2017. We have included all NIFTP cases (n = 6) and randomly selected cases of C-PTC (n = 14) and IFV-PTC (n = 8). Results: Comparing NIFTP and C-PTC cases, NIFTP cases showed significantly less papillary or pseudopapillary architecture, more bidimensional groups and microfollicles, and less tridimensionality, giant cells, and nuclear folds. We observed a trend towards significance for smear cellularity and amount of cytoplasm. Presence of nuclear folds was the only significant difference between NIFTP and IFV-PTC cases. The differences between groups in percent papillary or pseudopapillary architecture, cellularity, and tridimensionality showed a trend towards significance. Amount of colloid, dirty background, pleomorphism or atypia, nuclear pseudoinclusions, type of chromatin, and nucleolus were not significant. Conclusions: No cytopathological feature can differentiate between invasive and encapsulated IFV-PTC. In accordance with the recently accepted category, PTC smears with cells arranged in a predominantly follicular architecture should be reported as Bethesda IV category with descriptive terms to avoid false-positive cases.

Noninvasive follicular thyroid neoplasm with papillary-like nuclear features: a problematic entity

“…However, studies suggest that ultrasonography is insufficient for differentiating NIFTP from invasive EFVPTC (80,81,83). Both tumours show a similar appearance in cytological examinations as well (58,76,80,83,84). This is not surprising given that NIFTP can be differentiated from invasive EFVPTC by the exclusion of capsular and vascular invasion based on histological examination of the entire tumour along with the capsule (4,35).…”

Noninvasive Follicular Thyroid Neoplasm with Papillary-like Nuclear Features (NIFTP): Tumour Entity with a Short History. A Review on Challenges in Our Microscopes, Molecular and Ultrasonographic Profile

“…After NIFTP was introduced as a new entity, many studies on the cytology of NIFTP have been published. Several studies on cytological diagnostic features showed that features related to NIFTP differ mainly from PTC cytopathology and to lesser extent from FVPTC cytopathology [ 67 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 , 91 , 92 ].…”

“…On the other hand, microfollicles were more frequent in NIFTP than in PTC. On nuclear level, chromatin clearing, contour irregularities, enlargement, grooves, and pseudoinclusions were statistically significantly more expressed in PTC cases than in NIFTP cases [ 67 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 , 91 , 92 , 93 ].…”

Cytomorphology of Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features and the Impact of New Nomenclature on Molecular Testing

“…The identification of a potential NIFTP after a cytology review will help plan for discussions with the patient and support a more conservative surgery. Various studies have looked into the Bethesda categories where NIFTP has eventually been diagnosed to identify differences in cytological classification [8,10,12,13,19,20,21,23,24,25,26,27,28,29,30,31,32,33,34,35,36]. In the studies conducted in the US that have utilized contemporary NIFTP criteria, more than 80% of the diagnoses fall under the AUS, SFN and SUS categories [12,19,20,21,30,31,33].…”

“…The identification of the differences in cytology between NIFTP and I-FVPTC remains challenging. While a single study found more nuclear folds in I-FVPTC [29], others have found no distinguishing features in cytology [29,39]. Larger studies are needed in this area but given the significant overlap with its invasive counterpart, the accurate determination of NIFTP in cytology may be difficult to impossible in general practice.…”