title: Invasion rather than nuclear features correlates with outcome in encapsulated follicular tumors: further evidence for the reclassification of the encapsulated papillary thyroid carcinoma follicular variant.
abstract: The prognosis of the encapsulated follicular variant of papillary thyroid carcinoma (EFVPTC) and its relationship to encapsulated follicular carcinoma (EFC) and follicular adenoma (FA) is subject to controversy. All EFVPTCs, EFCs, and FAs identified at a single institution between 1981 and 2003 were analyzed microscopically. A cohort of FAs from a different hospital was also examined. EFVPTCs were subdivided into noninvasive EFVPTC (NIEFVPTC) and invasive EFVPTC (IEFVPTC) displaying capsular/vascular invasion. There were 83 EFVPTCs (57 noninvasive, 26 invasive), 14 EFCs, and 52 FAs. Similar to FA, over a median follow-up of 9.5 years, none of the NIEFVPTCs manifested lymph node metastasis (LNM) or recurred. Furthermore, with a median follow-up of 10.5 years, none of 39 NIEFVPTCs without radioactive iodine therapy recurred. Four (15%) of 26 IEFVPTCs and none of 14 EFCs harbored distant metastasis (P = .29). There was no difference in LNM rate and degree of vascular or capsular invasion between IEFVPTC and EFC (P > .1). All 4 IEFVPTCs with adverse behavior presented with distant metastasis and no LNM. Sixteen percent of IEFVPTCs had poor outcome, whereas there was none in the NIEFVPTCs (P = .007). In conclusion, NIEFVPTC seems to behave similarly to FA, whereas IEFVPTC can metastasize and spread like EFC. Thus, invasion rather than nuclear features drives outcome in encapsulated follicular tumors. Non-IEFVPTC could be treated in a conservative manner sparing patients unnecessary total thyroidectomy and radioactive iodine therapy. The position of the EFVPTC in the classification of thyroid neoplasia should be reconsidered.
authors.affiliation: Department of Surgery, Memorial Sloan-Kettering Cancer Center, New York, NY 10065.
authors.forename: Ian
authors.initials: I
authors.lastname: Ganly
authors.affiliation: Department of Surgery, Memorial Sloan-Kettering Cancer Center, New York, NY 10065.
authors.forename: Laura
authors.initials: L
authors.lastname: Wang
authors.affiliation: Department of Medicine, Endocrinology Service, Memorial Sloan-Kettering Cancer Center, New York, NY 10065.
authors.forename: R Michael
authors.initials: RM
authors.lastname: Tuttle
authors.affiliation: Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York, NY 10065.
authors.forename: Nora
authors.initials: N
authors.lastname: Katabi
authors.affiliation: Department of Surgery, "Dr. A. Oñativia" Hospital, Salta, Argentina.
authors.forename: Gustavo A
authors.initials: GA
authors.lastname: Ceballos
authors.affiliation: Pathology Unit, "Dr. A. Oñativia" Hospital, Salta, Argentina.
authors.forename: H Ruben
authors.initials: HR
authors.lastname: Harach
authors.affiliation: Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York, NY 10065. Electronic address: ghosseir@mskc.org.
authors.forename: Ronald
authors.initials: R
authors.lastname: Ghossein
mesh_terms: D000328:Adult; D000368:Aged; D002277:Carcinoma / Q000145:classification / Q000473:pathology*; D002291:Carcinoma, Papillary; D018265:Carcinoma, Papillary, Follicular; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D009364:Neoplasm Recurrence, Local / Q000473:pathology*; D011379:Prognosis; D000077273:Thyroid Cancer, Papillary; D013964:Thyroid Neoplasms / Q000145:classification / Q000473:pathology*; D013965:Thyroidectomy / Q000379:methods
keywords: Carcinomas; Encapsulated; Follicular variant; Papillary; Thyroid