Lésions thyroïdiennes folliculaires encapsulées, classifications histologique et pTNM, examen extemporané et évaluation histopathologique

Abstract

AbstractEncapsulated follicular-patterned thyroid tumors remain the daily challenge for pathologists, including experts. The differential diagnosis typically includes hyperplastic/adenomatous nodule, follicular adenoma, follicular carcinoma, follicular variant of papillary thyroid carcinoma (FVPTC), and non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP). The latter is a new terminology that was integrated into the WHO 2017 classification of endocrine tumors to replace the majority of non-invasive encapsulated FVPTC. Capsular and/or vascular invasion remains the main sign of malignancy. This invasion is, in the majority of cases, microscopic and necessitating an examination of the entire capsule. And for this reason, the frozen section is most often useless. The risk of recurrence and mortality correlates more with the importance of vascular invasion than with the size of the tumor and the management of these lesions must be discussed on a case-by-case basis and should not depend solely on the pTNM stage.