A modified reporting approach for thyroid FNA in the NIFTP era: A 1-year institutional experience.

BACKGROUND: The reclassification of noninvasive follicular variant of papillary thyroid carcinoma as noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) has created diagnostic and management issues for thyroid fine-needle aspiration (FNA). In response to these challenges, the authors' laboratory adopted a NIFTP policy including 1) stringent criteria (requiring pseudo-inclusions, papillae, and/or psammoma bodies) for a malignant diagnosis of papillary carcinoma to limit false-positive results due to NIFTP and 2) the use of explanatory notes in cases with cytomorphologic features suggestive of possible NIFTP to encourage lobectomy over thyroidectomy. This study examined the effects of this policy on FNA classification and subsequent surgical management.

METHODS: All thyroid FNAs performed at Brigham and Women's Hospital (n = 1300) during a 1-year period were evaluated for changes in the use of diagnostic categories, explanatory NIFTP notes, and surgical follow-up in comparison with historical controls.

RESULTS: The use of specific Bethesda categories did not significantly change. Only a single case of NIFTP was mistakenly classified as malignant. NIFTP was seldom suspected prospectively (17 of 1300; 1.3%); when NIFTP was suspected, cases were reported as suspicious for a follicular neoplasm/follicular neoplasm (n = 10) or suspicious for malignancy (SUS; n = 7). Five of the 7 SUS cases (71%) underwent partial thyroidectomy, compared to 19% of those classified as SUS without an explanatory NIFTP note (P < .02).

CONCLUSIONS: Thyroid FNA reporting modifications due to NIFTP affect only a small subset of specimens. When NIFTP is suspected, an explanatory note promotes limited surgical excision. More stringent criteria for malignancy affect few cases while potentially limiting false-positive diagnosis due to NIFTP. Cancer Cytopathol 2017;125:854-64. © 2017 American Cancer Society.