Adey FelekeTesfaye SisayRawleigh HoweEsmael Besufikad2025-08-312025-08-312023-12-22https://etd.aau.edu.et/handle/123456789/7230Breast cancer is the most common type of cancer in the world as well as in Ethiopia. Although research on breast cancer in Ethiopia has been conducted, none of them have evaluated breast cancer in multiple regions of the country, which is important considering Ethiopia’s enormous ethnic and genetic diversity. Hence, this study was carried out to evaluate the distribution of breast cancer subtypes and associated immune cell biomarkers, hormone receptors, matrix metalloproteinases (MMPs), and HPV genotypes in selected Ethiopian regions. A total of 227, 81, 58, and 120 formalin-fixed paraffin-embedded (FFPE) tissue blocks were collected for breast cancer subtyping, immune cell biomarkers analysis, MMP expression, and HPV genotyping, respectively. Immunohistochemistry (IHC) staining was performed for breast cancer subtyping based on estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER-2), and Ki-67 proliferation markers, and for additional immune cell biomarker expression. RNA was extracted and quantitative reverse-transcription PCR was performed for MMP expression analysis. DNA was extracted from archived FFPE breast tissue specimens and target genes were amplified using PCR for HPV genotyping. SPSS Version 25 was used to enter and analyze data. For immune cell biomarkers and MMP results, GraphPad Prism version 8.0.0 was used for statistical analysis. A large percentage of breast cancers were found to have advanced clinical and pathologic features, such as substantial lymph node involvement, large tumor size, and high histological grade. The percentage of ER and PR-negative tumors were 48.3% and 53.2%, respectively. The IHC subtype distribution was 33.1% triple-negative (ER-, PR-, HER-2-) breast cancer, 27.6% luminal B ((ER+, PR+, HER-2- and Ki-67 ≥ 20%) or (ER+, PR+, and HER-2+)), 25.2% luminal A (ER+, PR+, HER-2- and Ki-67< 20%), and 14.1% HER-2- enriched (ER-, PR-, HER-2+). In multiple logistic regression analysis, grade III and HER- 2 positivity were associated with larger tumor size, and tumor size was also higher in samples from Southwestern Ethiopia (Jimma) as compared to Northern Ethiopia (Mekele). The MMP-11 expression levels were significantly higher in breast cancer cases than in benign breast tumors (P=0.012). The non-luminal (triple-negative and HER-2-enriched) breast cancer subtype had a higher percentage of stromal CD20+, intratumoral CD3+ tumor-infiltrating lymphocytes, and CD68+ tumor-associated macrophages than the luminal (Luminal A and Luminal B) subtype. The stromal programmed cell death ligand 1 (PD-L1) +, intratumoral CD3+ tumor-infiltrating lymphocytes, CD163+ tumor-associated macrophages, and PD-L1+ were also more commonly found in grade III breast cancer than in grade I and II breast cancer, respectively. Human papillomavirus was found in 20.6% of breast cancer patients and 29.6% of non-malignant breast tumors. Human papillomavirus infection was nearly 10-fold more common in ER-positive than ER-negative breast cancer. A considerably high prevalence of triple-negative breast cancer was reported in our study, demanding additional research that includes identifying genetic predisposition factors. A significant association was found between the breast cancer subtype and stromal CD20+, intratumoral CD3+ tumor-infiltrating lymphocytes, and CD68+ tumor-associated macrophages. The stromal PD-L1+, intratumoral CD3+ tumor-infiltrating lymphocytes, CD163+ tumor-associated macrophages, and PD-L1+ were also associated with tumor grade. Our findings suggest an important impact of MMPs in breast cancer pathophysiology, particularly MMP-11. This study also showed no proof of a link between HPV infection and breast cancer; however, the finding that HPV was more prevalent in breast tumors that were ER-positive than ER-negative warrants further attention.enBreast CancerEstrogen ReceptorHER-2HPV GenotypeIHC SubtypeImmunohistochemistryMMPTumor-Associated MacrophagesTumor-Infiltrating Lymphocytesand Triple-NegativeThesis