Non-Invasive Follicular Thyroid Neoplasm With Papillary-Like Nuclear Features – An Illustrative Case

A 54-year-old woman underwent total thyroidectomy for a one-year history of anterior neck mass. The specimen was a 29.88–gram thyroid gland that on sectioning showed a single 2.0 x 1.5 x 1.5 cm encapsulated nodule with tan-brown solid cut surfaces noted on the right thyroid lobe. No gross lesions were noted on sectioning of the isthmus and left thyroid lobe. Microscopic examination showed a thinly encapsulated nodule composed of tightly-packed follicles. (Figure 1) Examination of the entire capsule did not show capsular or vascular invasion. The follicles were lined by follicular cells that had crowded and enlarged nuclei with pale chromatin and some nuclear membrane irregularities such as grooving. (Figure 2) There were no papillae, psammoma bodies, necrosis, mitotic figures and solid or trabecular architecture seen. Based on these features, the diagnosis rendered was non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP). NIFTP is a term adopted in 2016 to replace the nomenclature of a thyroid tumor previously termed “non-invasive encapsulated follicular variant of papillary thyroid carcinoma (FVPTC)”.1 In the most recent edition of the World Health Organization (WHO) Classification of Tumors, NITFP is considered a low-risk follicular cell-derived neoplasm whose definition also reflects the diagnostic criteria of this tumor.2