title: Follicular Thyroid Carcinoma: How Have Histologic Diagnoses Changed in the Last Half-Century and What Are the Prognostic Implications?
abstract: BACKGROUND
  Follicular thyroid carcinoma (FTC) comprises 10% of differentiated thyroid cancers. Diagnostic controversy and interobserver variability render the practical diagnosis of FTC difficult. Overall survival rates vary (46-97%). The aims of this study were to review FTC histologically at the authors' tertiary care institution and to evaluate long-term survival and recurrence.
  
  
  METHODS
  Diagnostic slides from 66 FTC cases (1965-2007) were reviewed by three pathologists from two institutions (blinded to clinical outcomes), and consensus was obtained. Patient demographics, tumor characteristics, and treatment, survival, and recurrence data were collected. Thyroid cancer-specific and recurrence-free survival were calculated by original and reclassified diagnoses.
  
  
  RESULTS
  Forty-seven cases (71%) were reclassified: 24 (36%) to papillary thyroid carcinoma (PTC), 18 (27%) to follicular adenoma (FA), and five (8%) to poorly differentiated carcinoma (PDC). Nineteen (29%) maintained a diagnosis of FTC. The extent of surgical resection and rates of radioiodine treatment did not differ by reclassification diagnosis. Pre-review FTC-specific survival was 83.5% and 75.1% at 10 and 20 years, respectively. Following contemporary reclassification, FTC-specific survival was 77% and 33.7% at 10 and 20 years, respectively. There were no cancer-specific deaths in the FA or PTC groups.
  
  
  CONCLUSIONS
  Over the past 50 years, changes in our understanding of the pathogenesis, histology, and behavior of thyroid carcinoma may partially account for the changes in histologic diagnosis. Elimination of PTC and FA "contaminants" led to decrease in survival following reclassification. Variability in histologic interpretation contributes to diagnostic challenges in follicular lesions. Histologic review of thyroid tumors for research studies is crucial, especially given the ever-changing diagnostic criteria.
authors.affiliation: 1 Department of Pathology, The University of Chicago , Chicago, Illinois.
authors.forename: Nicole A
authors.initials: NA
authors.lastname: Cipriani
authors.affiliation: 2 Department of Surgery, Oakland University William Beaumont School of Medicine , Royal Oak, Michigan.
authors.forename: Sapna
authors.initials: S
authors.lastname: Nagar
authors.affiliation: 3 Department of Surgery, Endocrine Surgery Research Program, The University of Chicago , Chicago, Illinois.
authors.forename: Sharone P
authors.initials: SP
authors.lastname: Kaplan
authors.affiliation: 3 Department of Surgery, Endocrine Surgery Research Program, The University of Chicago , Chicago, Illinois.
authors.forename: Michael G
authors.initials: MG
authors.lastname: White
authors.affiliation: 1 Department of Pathology, The University of Chicago , Chicago, Illinois.
authors.forename: Tatjana
authors.initials: T
authors.lastname: Antic
authors.affiliation: 4 Department of Pathology, Massachusetts General Hospital , Boston, Massachusetts.
authors.forename: Peter M
authors.initials: PM
authors.lastname: Sadow
authors.affiliation: 5 Department of Health Studies, The University of Chicago , Chicago, Illinois.
authors.forename: Briseis
authors.initials: B
authors.lastname: Aschebrook-Kilfoy
authors.affiliation: 3 Department of Surgery, Endocrine Surgery Research Program, The University of Chicago , Chicago, Illinois.
authors.forename: Peter
authors.initials: P
authors.lastname: Angelos
authors.affiliation: 3 Department of Surgery, Endocrine Surgery Research Program, The University of Chicago , Chicago, Illinois.
authors.forename: Edwin L
authors.initials: EL
authors.lastname: Kaplan
authors.affiliation: 3 Department of Surgery, Endocrine Surgery Research Program, The University of Chicago , Chicago, Illinois.
authors.forename: Raymon H
authors.initials: RH
authors.lastname: Grogan
mesh_terms: D018263:Adenocarcinoma, Follicular / Q000473:pathology*; D000236:Adenoma / Q000473:pathology*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002291:Carcinoma, Papillary / Q000473:pathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010818:Practice Patterns, Physicians' / Q000639:trends*; D011379:Prognosis; D013964:Thyroid Neoplasms / Q000473:pathology*; D055815:Young Adult