Impact of Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Features on Adequacy Criteria and Risk of Malignancy of Thyroid Fine-Needle Aspiration

Abstract

Objectives: The impact of noninvasive follicular thyroid neoplasm with papillary-like features (NIFTP) on nondiagnostic and benign diagnoses is not well characterized. Methods: The results of all thyroid fine-needle aspirates (FNAs) performed from 1997 to June 2016 with corresponding resections were reviewed. Results: From 12,764 aspirates, there were 8,106 (64%) benign diagnoses with 412 (5%) resections and 1,888 (14.8%) nondiagnostic diagnoses with 329 (17%) resections. Before the use of NIFTP, there were 18 (4.3%) malignancies in the benign aspirates and 39 (11.9%) malignancies in the nondiagnostic aspirates. There were 12 NIFTP cases on review. After reclassification using NIFTP, there were 10 of 412 (2.4%) malignancies in the benign aspirates. When cases with 10 to 60 benign follicle cells without atypia or Hürthle cell change werere classified as benign rather than nondiagnostic, the malignancy rate for a benign aspirate decreased (12/506, 2.3%; P = 1.0) when NIFTP cases were recognized. Conclusions: With NIFTP, reducing the threshold for adequacy from 60 to 10 cells led to nonsignificant decrease in the risk of malignancy of a benign diagnosis (2.4% to 2.3%). Thyroid fine-needle aspirates with 10 to 60 benign cells without atypia or Hürthle cell change should be diagnosed as benign.