HADFI Chaima, RAIS Mohamed El Akram2025-09-212025-09-212025-06-12http//localhost:8080/jspui/handle/123456789/13127The female breast, located between the 2nd and 6th ribs and attached to the pectoralis major by Cooper’s ligaments, is composed of skin, subcutaneous fat, and glandular tissue organized into 15–20 lobes that drain into lactiferous ducts, with most tissue concentrated in the upper outer quadrant. Breast cancer, the most frequently diagnosed cancer globally and the second leading cause of cancer-related deaths in women, is expected to affect 3.2 million women annually by 2050. The etiology and risk factors of breast cancer, highlighting the interplay between genetics, hormones, environment, and family history. Breast cancer arises from genetic mutations, hormonal dysregulation, and disrupted cell signaling. Its progression involves transition from preinvasive to invasive stages, with subtypes (DCIS, IDC, ILC) differing in behavior. Tumor biology (HR/HER2 status) guides treatment, while staging determines prognosis and therapy. TNBC remains the most challenging subtype due to limited targeted options. Advances in molecular profiling continue to refine personalized treatment strategies. This study examined the immunohistochemistry features of breast cancer, the most common cancer among women in Tebessa, Algeria. We examined patient demographics and clinical pathology. The relationship between molecular subgroups and clinicopathological characteristics was investigated. These findings demonstrate that breast cancer usually manifests in middle adulthood and that the luminal B subtype of the disease is more prevalent in this area of Algeria. Unclassifiable tumours had less aggressive clinical features. Tebessa will use the study's findings to create efficient screening programmes and cancer prevention plans.enBreast cancer, Molecular subtypes, Immunohistochemistry, Treatment, and Tumor biology.Thesis