title: Effect of Ki-67 on Immunohistochemical Classification of Luminal A to Luminal B Subtypes of Breast Carcinoma.
abstract: It has recently been proposed to include an immunohistochemical marker of cell proliferation, Ki-67, as an element with which to classify the molecular subtypes of breast cancer. The objective of this study was to evaluate the effect of the introduction of the Ki-67 marker on the molecular classification of breast cancer by immunohistochemistry. This study was performed on 234 cases of invasive ductal carcinoma of the breast submitted to two immunohistochemical classification panels, one including Ki-67 and the other not. The data obtained with the two classifications were correlated with well-established prognostic factors such as histologic grade, the number of lymph nodes affected and tumor size. The molecular classification without Ki-67 identified: 136 cases of luminal A (58.1%), 19 cases of luminal B (8.1%), 27 cases of human epidermal growth-factor receptor 2 overexpressing (11.5%), 27 cases of basal-like (11.5%), and 25 cases of nonbasal-like triple-negative tumors (10.7%). When Ki-67 was included, this situation changed significantly, with the following cases being identified: 72 cases of luminal A (30.8%) and 83 cases of luminal B tumors (35.5%), resulting in a Kappa score of 0.216. Evaluation of correlations between the luminal A and luminal B tumor subtypes and the selected prognostic factors showed a statistically significant difference only when Ki-67 was included and only with respect to histologic grade (p < 0.001). The new classification with Ki-67 significantly altered the prevalence of the luminal A and luminal B subtypes and improved correlation with the histologic grade.
authors.affiliation: Biomedical of Pathology Department, Teaching Hospital, Federal University of Goiás, Goiânia, Goiás, Brazil.
authors.forename: Magno Belém
authors.initials: MB
authors.lastname: Cirqueira
authors.affiliation: Pathology Department, Federal University of Goiás, Goiânia, Goiás, Brazil.
authors.forename: Marise Amaral Rebouças
authors.initials: MA
authors.lastname: Moreira
authors.affiliation: Gynecology and Obstetrics Department, Federal University of Goiás, Goiânia, Goiás, Brazil.
authors.forename: Leonardo Ribeiro
authors.initials: LR
authors.lastname: Soares
authors.affiliation: Pathology Department, Federal University of Goiás, Goiânia, Goiás, Brazil.
authors.forename: Maria-Auxiliadora de Paula Carneiro
authors.initials: MA
authors.lastname: Cysneiros
authors.affiliation: Pathology Department, Federal University of Goiás, Goiânia, Goiás, Brazil.
authors.forename: Maria-Helena Tavares
authors.initials: MH
authors.lastname: Vilela
authors.affiliation: Gynecology and Breast Service of Hospital Araújo Jorge of the Associação de Combate ao Câncer de Goiás (ACCG), Gynecology and Obstetrics Department, Federal University of Goiás, Goiânia, Goiás, Brazil.
authors.forename: Ruffo
authors.initials: R
authors.lastname: Freitas-Junior
mesh_terms: D014408:Biomarkers, Tumor / Q000378:metabolism*; D001943:Breast Neoplasms / Q000145:classification* / Q000378:metabolism* / Q000473:pathology; D002277:Carcinoma / Q000145:classification* / Q000378:metabolism* / Q000473:pathology; D005260:Female; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D019394:Ki-67 Antigen / Q000378:metabolism*; D060787:Neoplasm Grading; D009367:Neoplasm Staging
chemical_list: D014408:Biomarkers, Tumor; D019394:Ki-67 Antigen
keywords: Ki-67; breast cancer; classification; immunohistochemistry; molecular subtypes