title: Inter-Observer Variation in the Pathologic Identification of Minimal Extrathyroidal Extension in Papillary Thyroid Carcinoma.
abstract: BACKGROUND
  Extrathyroidal extension (ETE) is a significant prognostic factor in papillary thyroid carcinoma (PTC). Minimal extrathyroidal extension (mETE) is characterized by involvement of the sternothyroid muscle or perithyroid soft tissue, and is generally identified by light microscope examination. Patients with mETE, identified pathologically, are automatically upstaged to pT3. However, the prognostic implications of mETE have been a source of controversy in the literature. Moreover, there is also controversy surrounding the identification of mETE on pathological specimens. The objective of this study was to determine the level of agreement among expert pathologists in the identification of mETE in PTC cases.
  
  
  METHODS
  Eleven expert pathologists from the United States, Italy, and Canada were asked to perform a review of 69 scanned slides of representative permanent sections of PTC specimens. Each slide was evaluated for the presence of mETE. The pathologists were also asked to list the criteria they use to identify mETE.
  
  
  RESULTS
  The overall strength of agreement for identifying mETE was slight (κ = 0.14). Inter-pathologist agreement was best for perithyroidal skeletal muscle involvement (κ = 0.46, moderate agreement) and worst for invasion around thick-walled vascular structures (κ = 0.02, slight agreement). In addition, there was disagreement over the constellation of histologic features that are diagnostic for mETE, which affected overall agreement for diagnosing mETE.
  
  
  CONCLUSIONS
  Overall agreement for the identification of mETE is poor. Disagreement is a result of both variation in individual pathologists' interpretations of specimens and disagreement on the histologic criteria for mETE. Thus, the utility of mETE in staging and treatment of PTC is brought into question. The lack of concordance may explain the apparent lack of agreement regarding the prognostic significance of this pathologic feature.
authors.affiliation: 1 Department of Otolaryngology-Head and Neck Surgery, Thyroid, Head and Neck Cancer (THANC) Foundation , New York, New York.
authors.forename: Henry K
authors.initials: HK
authors.lastname: Su
authors.affiliation: 2 Department of Pathology, Mount Sinai Beth Israel, New York, New York.
authors.forename: Bruce M
authors.initials: BM
authors.lastname: Wenig
authors.affiliation: 1 Department of Otolaryngology-Head and Neck Surgery, Thyroid, Head and Neck Cancer (THANC) Foundation , New York, New York.
authors.forename: Grace C
authors.initials: GC
authors.lastname: Haser
authors.affiliation: 1 Department of Otolaryngology-Head and Neck Surgery, Thyroid, Head and Neck Cancer (THANC) Foundation , New York, New York.
authors.forename: Meghan E
authors.initials: ME
authors.lastname: Rowe
authors.affiliation: 3 Department of Pathology, Laboratory Medicine Program, Toronto General Hospital , Toronto, Canada .
authors.forename: Sylvia L
authors.initials: SL
authors.lastname: Asa
authors.affiliation: 4 Department of Pathology and Laboratory Medicine, Hospital of the University of Pennsylvania , Philadelphia, Pennsylvania.
authors.forename: Zubair
authors.initials: Z
authors.lastname: Baloch
authors.affiliation: 5 Department of Otorhinolaryngology-Head and Neck Surgery, Montefiore Medical Center, Albert Einstein College of Medicine , Bronx, New York.
authors.forename: Eugenie
authors.initials: E
authors.lastname: Du
authors.affiliation: 6 Department of Pathology, Massachusetts General Hospital , Boston, Massachusetts.
authors.forename: William C
authors.initials: WC
authors.lastname: Faquin
authors.affiliation: 7 Centro Consulenze Anatomia Patologica Oncologica, Centro Diagnostico Italiano , Milan, Italy .
authors.forename: Giovanni
authors.initials: G
authors.lastname: Fellegara
authors.affiliation: 8 Department of Pathology, University of Michigan Medical School , Ann Arbor, Michigan.
authors.forename: Thomas
authors.initials: T
authors.lastname: Giordano
authors.affiliation: 9 Department of Pathology, Memorial Sloan-Kettering Cancer Center , New York, New York.
authors.forename: Ronald
authors.initials: R
authors.lastname: Ghossein
authors.affiliation: 4 Department of Pathology and Laboratory Medicine, Hospital of the University of Pennsylvania , Philadelphia, Pennsylvania.
authors.forename: Virginia A
authors.initials: VA
authors.lastname: LiVolsi
authors.affiliation: 10 Department of Pathology and Laboratory Medicine, University of Wisconsin , Madison, Wisconsin.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Lloyd
authors.affiliation: 3 Department of Pathology, Laboratory Medicine Program, Toronto General Hospital , Toronto, Canada .
authors.forename: Ozgur
authors.initials: O
authors.lastname: Mete
authors.affiliation: 11 Population Health Science and Policy, Mount Sinai Hospital , New York, New York.
authors.forename: Umut
authors.initials: U
authors.lastname: Ozbek
authors.affiliation: 7 Centro Consulenze Anatomia Patologica Oncologica, Centro Diagnostico Italiano , Milan, Italy .
authors.forename: Juan
authors.initials: J
authors.lastname: Rosai
authors.affiliation: 12 Department of Pathology, Medical College of Wisconsin , Milwaukee, Wisconsin.
authors.forename: Saul
authors.initials: S
authors.lastname: Suster
authors.affiliation: 13 Department of Pathology, Woodland Hills Medical Center , Woodland Hills, California.
authors.forename: Lester D
authors.initials: LD
authors.lastname: Thompson
authors.affiliation: 14 Department of Pathology, New York-Presbyterian/Columbia , New York, New York.
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Turk
authors.affiliation: 15 Department of Otolaryngology-Head and Neck Surgery , Mount Sinai Beth Israel , New York, New York.
authors.forename: Mark L
authors.initials: ML
authors.lastname: Urken
mesh_terms: D002277:Carcinoma / Q000150:complications / Q000175:diagnosis*; D002291:Carcinoma, Papillary / Q000150:complications / Q000175:diagnosis*; D006801:Humans; D009367:Neoplasm Staging / Q000379:methods; D015588:Observer Variation; D010336:Pathology / Q000379:methods* / Q000592:standards; D011379:Prognosis; D015203:Reproducibility of Results; D000077273:Thyroid Cancer, Papillary; D013961:Thyroid Gland / Q000473:pathology / Q000601:surgery; D013964:Thyroid Neoplasms / Q000150:complications / Q000175:diagnosis*; D013965:Thyroidectomy