Patients with Non-invasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features are Unlikely to have Malignant Preoperative Cytology.

BACKGROUND: The newly termed tumor 'noninvasive follicular thyroid neoplasm with papillary-like nuclear features' (NIFTP) acts in an indolent manner and can likely be safely managed with a thyroid lobectomy. Preoperative fine-needle aspiration (FNA) is the cornerstone of surgical planning, but the ability of FNA to distinguish NIFTP from other variants of papillary thyroid carcinoma (PTC) has not been well-evaluated.

METHODS: A 9-year retrospective review of the preoperative cytology and surgical pathology of PTC patients who underwent a thyroidectomy at our tertiary referral center.

RESULTS: Overall, 174 patients with 177 PTCs had a preoperative FNA followed by a thyroidectomy, and met our inclusion criteria. Of the 21 patients with NIFTP, the preoperative cytology was read as malignant in three (14%), suspicious for malignancy in three (14%), follicular neoplasm in ten (48%), atypia of undetermined significance in four (19%), and benign in one (5%) nodule. When comparing patients with NIFTP with other variants of PTC, patients with NIFTP were younger (p = 0.023) and less likely to have malignant cytology (p < 0.001). On multivariable regression modeling, malignant cytology was independently associated with a decreased risk of a final diagnosis of NIFTP (odds ratio 0.064, 95% confidence interval 0.018-0.233, p < 0.001).

CONCLUSIONS: Patients with a final diagnosis of NIFTP are less likely to have preoperative FNA diagnosis of malignancy than those with final pathology of classical or other variants of PTC. Surgeons should take this into consideration when considering between a lobectomy and total thyroidectomy for patients with suspected PTC.