title: Difference between Luminal A and Luminal B Subtypes According to Ki-67, Tumor Size, and Progesterone Receptor Negativity Providing Prognostic Information.
abstract: BACKGROUND
  The St. Gallen International Expert Consensus of 2011 proposes a new classification system for breast cancer based on its division into five subgroups. The criteria to identify these subtypes were recently refined at the 2013 Conference. In this respect, the authors of this paper have conducted a retrospective analysis of breast cancer subtypes, related to Ki-67 and involvement of the axillary lymph nodes (ALNs). The analysis was performed only in the cases of invasive breast cancer in the pT2 stages. The research and results of the paper have shown that investigating the value of these parameters could be of great benefit in future treatment strategies of invasive breast cancer.
  
  
  METHODS
  A retrospective analysis of breast cancer subtypes, tumor nodal metastatic staging, and histopathological grading of 108 cases has been performed according to the methods recommended and provided by the St. Gallen International Expert Consensus Report, 2011. The estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor-2 (HER2), and Ki-67 of 108 tumor samples were all investigated by immunohistochemistry according to the methods used to classify breast cancer subtypes as proposed in the St. Gallen Consensus Report, 2011. Invasive breast cancers (n = 108) were immunohistochemically classified as follows: 28 (25.92%) as Luminal A, 51 (47.22%) as Luminal B (HER2 negative), 21 (19.44%) as Luminal B-like (HER2 negative), 2 (1.85%) as HER2 positive, and 6 (5.55%) as being a triple-negative subtype.
  
  
  RESULTS
  The conclusion was made that when Ki-67 was found to be higher, patients also showed a higher involvement in their ALNs. The chi-square test shows the difference to be significant (chi-square = 4.757; P = 0.029). Luminal B subtypes had the highest percentage (54.9%) of involvement of lymph nodes when compared to the other four subtypes. The Luminal B subtype had a higher percentage (51.4%) of involvement of lymph nodes than did Luminal A (10.7%). The chi-square test also shows the difference to be significant (P < 0.05).
  
  
  CONCLUSIONS
  A combination of the Ki-67 index, HER negative tumors, PR negativity, and a low value that can be used to segregate ER positive pT2 tumors into prognostically significantly different clinical outcomes may be utilized clinically to guide patient management in accordance with these tumor characteristics.
authors.affiliation: Institute for Oncology and Radiology of Serbia, Belgrade, Serbia.
authors.forename: Zorka
authors.initials: Z
authors.lastname: Inic
authors.affiliation: Institute for Oncology and Radiology of Serbia, Belgrade, Serbia.
authors.forename: Milan
authors.initials: M
authors.lastname: Zegarac
authors.affiliation: Institute for Oncology and Radiology of Serbia, Belgrade, Serbia.
authors.forename: Momcilo
authors.initials: M
authors.lastname: Inic
authors.affiliation: Institute for Oncology and Radiology of Serbia, Belgrade, Serbia.
authors.forename: Ivan
authors.initials: I
authors.lastname: Markovic
authors.affiliation: Institute for Oncology and Radiology of Serbia, Belgrade, Serbia.
authors.forename: Zoran
authors.initials: Z
authors.lastname: Kozomara
authors.affiliation: Institute for Oncology and Radiology of Serbia, Belgrade, Serbia.
authors.forename: Igor
authors.initials: I
authors.lastname: Djurisic
authors.affiliation: Institute for Oncology and Radiology of Serbia, Belgrade, Serbia.
authors.forename: Ivana
authors.initials: I
authors.lastname: Inic
authors.affiliation: Institute for Oncology and Radiology of Serbia, Belgrade, Serbia.
authors.forename: Gordana
authors.initials: G
authors.lastname: Pupic
authors.affiliation: Institute for Pathology, Faculty of Medicine University of Kragujevac, Serbia.
authors.forename: Snezana
authors.initials: S
authors.lastname: Jancic
keywords: Ki-67; Luminal A; Luminal B; breast cancer; positive lymph node status; prognostic information