title: Encapsulated Thyroid Carcinoma of Follicular Cell Origin.
abstract: Encapsulated carcinomas of follicular cell origin are subject to considerable controversies. This group includes an encapsulated/well-circumscribed (E/WC) follicular variant of papillary carcinoma (FVPTC) and encapsulated follicular and Hurthle cell carcinoma (EFC, EHC respectively). FVPTC usually presents as an E/WC tumor and less commonly as an infiltrative neoplasm. E/WC FVPTC rarely metastasizes to lymph nodes, whereas infiltrative tumors often present with cervical nodal metastases. Many studies revealed FVPTC in general to be genetically close to the follicular adenomas (FA)/EFC group of tumors. This is particularly true for the E/WC FVPTC which has a high rate of RAS and lack BRAFV600E mutations. Infiltrative FVPTC has an opposite molecular profile closer to classical papillary carcinoma than to FA/EFC (BRAFV600E > RAS mutations). Noninvasive E/WC FVPTCs are extremely indolent even if treated with lobectomy alone. While EFC and EHC with capsular invasion only have an excellent outcome, those with extensive (≥4 foci) lymphovascular invasion (LVI) have a significant rate of distant recurrence. The prognosis of those with focal LVI seems good, but more studies are needed to confirm their behavior. In EHC, those with extensive/significant LVI have a different RNA expression profile than those with less LVI. EHC appear to recur earlier, are less RAI avid, and have a different mutation profile than EFC. Noninvasive E/WC FVPTC should be treated conservatively. There is therefore a need to reclassify the E/WC FVPTC in order to prevent overtreatment. In view of their molecular and behavioral differences, EHC should not be considered a subset of EFC.
authors.affiliation: Department of Pathology, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY, 10065, USA.
authors.forename: Bin
authors.initials: B
authors.lastname: Xu
authors.forename: Ronald
authors.initials: R
authors.lastname: Ghossein
mesh_terms: D018263:Adenocarcinoma, Follicular / Q000175:diagnosis / Q000401:mortality / Q000473:pathology* / Q000628:therapy; D018249:Adenoma, Oxyphilic; D006801:Humans; D008207:Lymphatic Metastasis; D009361:Neoplasm Invasiveness; D009364:Neoplasm Recurrence, Local; D016019:Survival Analysis; D013964:Thyroid Neoplasms / Q000175:diagnosis / Q000401:mortality / Q000473:pathology* / Q000628:therapy