title: Observer variation in the diagnosis of follicular variant of papillary thyroid carcinoma.
abstract: The histopathologic diagnosis of follicular variant of papillary thyroid carcinoma (FVPCA) can be difficult. Recent reports have suggested that this neoplasm may be frequently overdiagnosed by pathologists. We examined the observer variation in the diagnosis of FVPCA in 87 tumors by 10 experienced thyroid pathologists. The criteria that the reviewers considered most helpful for making a diagnosis of FVPCA were also assessed. A concordant diagnosis of FVPCA was made by all 10 reviewers with a cumulative frequency of 39%. In this series, 24.1% of the patients had metastatic disease (n = 21). In the cases with metastatic disease, a diagnosis of FVPCA was made by all 10 reviewers with a cumulative frequency of 66.7%, and 7 of the reviewers made a diagnosis of FVPCA with a cumulative frequency of 100%. The most important criteria used to diagnose FVPCA included the presence of cytoplasmic invaginations into the nucleus (pseudo-inclusions), abundant nuclear grooves, and ground glass nuclei. These results suggest that although the diagnosis of FVPCA is variable even among experienced thyroid pathologists, most reviewers agreed on this diagnosis for patients with metastatic disease. The use of well-defined histopathologic features should improve the consistency in diagnosing FVPCA. Since most cases with metastatic disease had obvious invasion, caution should be used in making a diagnosis of FVPCA in the absence of the major histopathologic features or clear-cut invasive growth.
authors.affiliation: Department of Laboratory Medicine and Pathology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA. lloyd.ricardo@mayo.edu
authors.forename: Ricardo V
authors.initials: RV
authors.lastname: Lloyd
authors.forename: Lori A
authors.initials: LA
authors.lastname: Erickson
authors.forename: Mary B
authors.initials: MB
authors.lastname: Casey
authors.forename: King Y
authors.initials: KY
authors.lastname: Lam
authors.forename: Christine M
authors.initials: CM
authors.lastname: Lohse
authors.forename: Sylvia L
authors.initials: SL
authors.lastname: Asa
authors.forename: John K C
authors.initials: JK
authors.lastname: Chan
authors.forename: Ronald A
authors.initials: RA
authors.lastname: DeLellis
authors.forename: H Ruben
authors.initials: HR
authors.lastname: Harach
authors.forename: Kennichi
authors.initials: K
authors.lastname: Kakudo
authors.forename: Virginia A
authors.initials: VA
authors.lastname: LiVolsi
authors.forename: Juan
authors.initials: J
authors.lastname: Rosai
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Sebo
authors.forename: Manuel
authors.initials: M
authors.lastname: Sobrinho-Simoes
authors.forename: Bruce M
authors.initials: BM
authors.lastname: Wenig
authors.forename: Marick E
authors.initials: ME
authors.lastname: Lae
mesh_terms: D018265:Carcinoma, Papillary, Follicular / Q000473:pathology* / Q000556:secondary; D006801:Humans; D009361:Neoplasm Invasiveness; D015588:Observer Variation; D012189:Retrospective Studies; D013964:Thyroid Neoplasms / Q000473:pathology*