Noninvasive follicular thyroid neoplasm with papillary nuclear characteristics: Clinicopathologic features and follow-up

Financial support: None. Conflicts of interest: No conflicts of interest declared concerning the publication of this article. Submitted: November 01, 2018. Accepted: December 15, 2018. The study was carried out at Grupo Oroño, Unidad de Tiroides, Rosario, Argentina. abstract Introduction: A lesion structurally encapsulated or with noninfiltrating expansive edges, follicular pattern growth, <1% of papillary formation, no psammoma bodies, <30% of trabecular and/or insular solid growth, nuclear score 2-3, no invasion of the tumor capsule or the peritumoral vessels, no tumor necrosis and without high mitotic activity, was once called “papillary thyroid carcinoma (PTC) encapsulated follicular variant” and became “noninvasive follicular thyroid neoplasm with papillary nuclear features” (NIFTP). Objective: To review the operated follicular variant PTC. Materials and Methods: The cases were adapted to the new classification and the clinicopathologic and follow-up features in our patients with and without NIFTP were described. Results: In the follicular variant PTC, 19.3% (21/107) were NIFTP. The range of NIFTPs was between 5 and 50mm; mean ± ESM: 21.8 ± 3.5 mm; 3 NIFTP were larger (>40 mm). All were treated with total thyroidectomy and 20/21 received an ablative dose of I131. At the follow-up (>5 years on average), there were no cases of local, regional or systemic, biochemical or structural recurrences. Comparing the NIFTP and non-NIFTP, similar tumor features were found for the age, gender, maximum tumor dimension, surgical extension, and iodine ablation, median follow-up and recurrent events; p>0.05, without statistical significance. Conclusion: Twenty percent of follicular variant papillary carcinomas now reclassified as NIFTP were overtreated and overcontrolled as if they were PTC; no recurrent events or deaths were detected. We cannot distinguish whether the good prognosis is due to the nature of these neoplasms or to overtreatment.