"The other side of the coin": understanding noninvasive follicular tumor with papillary-like nuclear features in unifocal and multifocal settings.

The recent description of noninvasive follicular tumor with papillary-like nuclear features (NIFTP) creates several diagnostic and therapeutic challenges for both the pathologist and the attending clinician. Given the concern about overtreatment of these neoplasms, the best way to manage the patients by a surgical procedure and postsurgical follow-up is still under discussion. We aimed to identify predictors of synchronous disease (eg, bilateral cancers) that can influence the appropriate type of surgery and long-term surveillance. We reevaluated the original diagnosis and the presence of contralateral lesions in 94 cases retrieved from our archives that were seen between 2010 and 2017. In 74 cases, the diagnosis was NIFTP, and in 20 cases, the diagnosis was infiltrative follicular variant of papillary thyroid carcinoma (IFVPTC). Bilateral disease was found in 17% of the cases. In 13 (18%) of those cases, NIFTP was the primary lesion, and in 3 (15%), it was IFVPTC. The contralateral disease was predominantly invasive: 6 cases of micropapillary carcinoma, 5 of papillary thyroid carcinoma, 3 of IFVPTC, and 2 of NIFTP. Despite the higher frequency of contralateral disease in NIFTP, there was no statistically significant difference with IFVPTC. In the patients with multifocal NIFTP, 2 (15%) of the contralateral malignancies showed microscopic extrathyroidal extension (P < .05). We conclude that close monitoring of the contralateral lobe is appropriate in patients with FVPTC, particularly NIFTP, if they are not submitted to total thyroidectomy.