Immunohistochemical Characterization and Subclassification of Triple Negative Breast Cancer of Egyptian Female Patients

Abstract
Background: Triple negative breast cancer is representing a heterogeneous group of breast cancer. Many trials were carried out for its subclassification by different markers. This classification also could help in new treatment modalities.
Aim of Study: To investigate and identify additional possible prognostic markers that can help in subclassification of triple negative breast cancer.
Patients and Methods: This retrospective study included 59 women with triple negative breast cancer referred to NCI, Cairo University, Egypt. Clinical data were collected. Immu-nohistochemical analyses were performed for the assessment of CK5/6, Epithelial growth factor receptor (EGFR), and Claudin 4. All cases were followed-up with a median follow-up time 40.5 months (range: 8-67).
Results: Among the studied cases (71.2%) were positive to CK5/6, (45.8%) were positive to EGFR, (89.8%) represented Claudin4 high. Expression of CK5/6 revealed a significant relationship with tumor size. Expression of EGFR revealed a significant relationship with stage of the tumor. Most of cases of Claudin 4 high represented high grade, high stage and node positivity, but not reached the significant level. There is significant relationship found between grade and DFS, as well as OS with grade, stage, occurrence of metastasis and node positivity.
Conclusion: Triple negative breast cancer is a heteroge-neous molecular type of breast cancer. Basal markers such as CK5/6 and EGFR are used for identification of basal subgroup of TNBC. This subclassification of triple negative breast cancer helps in categorization of patients who are candidate for targeted therapy, such as tyrosine kinase inhibitors (TKIs) in cases positive for EGFR. Expression of Claudin 4 also helps in classification of triple negative breast cancer, and selection of cases that could be targeted by monoclonal antibodies.