Update on follicular variant of papillary thyroid carcinoma with an emphasis on new terminology: noninvasive follicular thyroid neoplasm with papillary-like nuclear features

The most common papillary thyroid carcinoma (PTC) variant is the follicular variant, representing ∼30% of all PTCs. The tumour is most common in middle aged (4th – 5th decades) women, who usually present with a single dominant nodule (about 3 cm). By definition, follicular architecture must be the dominant finding, while demonstrating the nuclear features of PTC. Papillary structures are <1% of volume, while necrosis, increased mitoses (>3/10 high power fields) and psammoma bodies are absent. The tumour category is divided into “encapsulated/well demarcated” and “invasive” types. The nuclear features include enlarged, elongated and overlapping nuclei; membrane irregularities (irregular contours, grooves and pseudoinclusions); chromatin clearing, margination and glassy nuclei. When the tumour is encapsulated/well demarcated without invasion, demonstrating the other inclusion and exclusion criteria, the new name of “Noninvasive Follicular Thyroid Neoplasm with Papillary-like Nuclear Features” (NIFTP) is used, a tumour that requires no additional treatment.