title: Diagnostic significance of cell kinetic parameters in World Health Organization type A and B3 thymomas and thymic carcinomas.
abstract: The prognostic importance of histologic classifications of thymic epithelial neoplasms is controversial. Evidence suggests that difficulties in reproducibility affect prognostic studies. Two thoracic pathologists independently classified 80 cases of type A or B3 thymoma and thymic carcinoma according to World Health Organization (WHO) classification. Ki-67 labeling index (LI) was used to identify cutoff points between WHO types. Recursive partitioning (Rpart) and ad hoc methods separated the data points. The pathologists agreed on type A (n = 31), type B3 (n = 21), and thymic carcinoma (n = 14). Ki-67 LI differed between types A and B3 (P < .001) and between thymic carcinoma and type A (P < .001) or type B3 (P = .001). Mitotic activity differed between thymic carcinoma and type A (P < .001) or type B3 (P < .001). Rpart revealed Ki-67 LI greater than 14.0% only in thymic carcinoma; cases with Ki-67 LI less than 5.1% did not represent thymic carcinoma. Ad hoc analysis showed Ki-67 LI greater than or equal to 13.5% represents thymic carcinoma; only type A had Ki-67 LI less than 2%. The pathologists disagreed on histologic type in 14 cases. In 11 of 14 cases with available Ki-67, the Rpart method predicted the WHO type; in 7 of 14 cases, the ad hoc method predicted the WHO type. In conclusion, Ki-67 LI is helpful in differentiating thymic epithelial neoplasms, with Ki-67 LI less than 2% and greater than or equal to 13.5% distinguishing type A thymoma and thymic carcinoma, respectively.
authors.affiliation: Department of Laboratory Medicine & Pathology, Mayo Clinic Rochester, MN, 55905, USA. Electronic address: roden.anja@mayo.edu.
authors.forename: Anja C
authors.initials: AC
authors.lastname: Roden
authors.affiliation: Department of Laboratory Medicine & Pathology, Mayo Clinic Rochester, MN, 55905, USA.
authors.forename: Eunhee S
authors.initials: ES
authors.lastname: Yi
authors.affiliation: Division of Biomedical Statistics and Informatics, Mayo Clinic Rochester, MN, 55905, USA.
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Jenkins
authors.affiliation: Department of Laboratory Medicine & Pathology, Mayo Clinic Rochester, MN, 55905, USA.
authors.forename: Janis L
authors.initials: JL
authors.lastname: Donovan
authors.affiliation: Division of General Thoracic Surgery, Mayo Clinic Rochester, MN, 55905, USA.
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Cassivi
authors.affiliation: Department of Radiation-Oncology, Mayo Clinic Rochester, MN, 55905, USA.
authors.forename: Yolanda I
authors.initials: YI
authors.lastname: Garces
authors.affiliation: Division of Medical Oncology, Mayo Clinic Rochester, MN, 55905, USA.
authors.forename: Randolph S
authors.initials: RS
authors.lastname: Marks
authors.affiliation: Department of Laboratory Medicine & Pathology, Mayo Clinic Rochester, MN, 55905, USA.
authors.forename: Marie-Christine
authors.initials: MC
authors.lastname: Aubry
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000032:analysis; D001706:Biopsy; D002277:Carcinoma / Q000473:pathology*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D019394:Ki-67 Antigen / Q000032:analysis; D007700:Kinetics; D008297:Male; D008875:Middle Aged; D008938:Mitosis; D008940:Mitotic Index; D015588:Observer Variation; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D013945:Thymoma / Q000737:chemistry / Q000145:classification / Q000473:pathology*; D013953:Thymus Neoplasms / Q000737:chemistry / Q000145:classification / Q000473:pathology*; D014944:World Health Organization; D055815:Young Adult
chemical_list: D014408:Biomarkers, Tumor; D019394:Ki-67 Antigen
keywords: Bcl-2; Ki-67 labeling index; Mitoses; Thymic carcinoma; Thymoma