Thyroid : official journal of the American Thyroid Association
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Background: The percentage of papillae is a crucial criterion in differentiating noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) from papillary thyroid carcinomas (PTCs) and in subclassifying PTC into classic and follicular variant. Since the description of NIFTP, three studies have shown that the presence of any papillae may be associated with nodal metastasis, which led to modification of the NIFTP criterion from <1% papillae to no true papillae allowed. We aim at providing clinical evidence-based data on the impact that papillary growth has on nodal spread and tumor genotype in tumors previously diagnosed as encapsulated unifocal PTC. ⋯ Nodal metastases were not seen in tumors with <1% papillae irrespective of invasive status. These findings indicate that the initial criterion of <1% papillae is still valid for the diagnosis of NIFTP. Reinstituting this criterion will spare a carcinoma diagnosis and unnecessary therapy with its side effects on patients who have negligible clinical risk.