Encapsulated Thyroid Carcinoma of Follicular Cell Origin

Endocr Pathol. 2015 Sep;26(3):191-9. doi: 10.1007/s12022-015-9376-5.

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.

Publication types

  • Review

MeSH terms

  • Adenocarcinoma, Follicular / diagnosis
  • Adenocarcinoma, Follicular / mortality
  • Adenocarcinoma, Follicular / pathology*
  • Adenocarcinoma, Follicular / therapy
  • Adenoma, Oxyphilic
  • Humans
  • Lymphatic Metastasis
  • Neoplasm Invasiveness
  • Neoplasm Recurrence, Local
  • Survival Analysis
  • Thyroid Neoplasms / diagnosis
  • Thyroid Neoplasms / mortality
  • Thyroid Neoplasms / pathology*
  • Thyroid Neoplasms / therapy

Supplementary concepts

  • Thyroid cancer, Hurthle cell