Noninvasive follicular thyroid neoplasm with papillary-like nuclear features: A distinct clinicopathologic entity.

Abstract

The objective of this study is to retrospectively evaluate follicular variant of papillary thyroid carcinoma (FVPTC) and reclassify encapsulated FVPTC as noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) according to the criteria proposed by The Endocrine Pathology Society working group in 2015 to correlate with outcome. Retrospective review of case records of all patients diagnosed as carcinoma of thyroid between 2015 and 2016 was done for the histologic subtype. Gross and microscopic features on resected specimens of FVPTC were reviewed and subtyped as invasive and encapsulated based on capsular/vascular invasion; the encapsulated forms were further studied for size, number, follicular architecture, nuclear features, presence of psammoma bodies, stromal fibrosis, necrosis, mitoses, and lymph node status. Out of the 383 patients with thyroid carcinomas in the study period, 349 were PTC which included 106 FVPTC. Thirty-three patients fulfilled the criteria to be labeled as NIFTP. Total thyroidectomy was performed in 8 patients and hemithyroidectomy in 25 patients. Lymph node dissection along with total thyroidectomy was done in 3 and completion thyroidectomy following hemithyroidectomy was done in 9. There were 29 single and 4 multiple lesions with size varying from 0.2 to 7 cm including 5 lesions measuring <1 cm. The involvement was confined to one lobe in 31 and both lobes in 2 specimens. Patients are on follow-up with no recurrence till date. Thyroid carcinomas currently diagnosed as FVPTC should be evaluated for criteria of NIFTP to avoid overtreatment as they have an indolent behavior.