Breast Cancer

Breast cancer is a malignant tumor arising from the epithelial cells of the breast, most commonly from the ductal or lobular epithelium. It is the most frequent cancer in women worldwide and has variable clinical presentations depending on stage and subtype.

Definition

Epidemiology

Most common cancer among women globally
Incidence increases with age; peak incidence between 50–70 years
Higher prevalence in developed countries due to lifestyle and screening
Risk factors include family history, genetic mutations (BRCA1/2, TP53), hormonal exposure, obesity, alcohol use, and nulliparity
Survival rates depend on stage, receptor status, and access to treatment

Etiology

Genetic mutations: BRCA1, BRCA2, TP53, PTEN
Hormonal factors: prolonged estrogen exposure (early menarche, late menopause, hormone replacement therapy)
Lifestyle factors: alcohol use, obesity, physical inactivity
Environmental factors: radiation exposure, endocrine disruptors
Family history and hereditary syndromes increase risk

Pathophysiology

Normal epithelial cells undergo genetic mutations leading to uncontrolled proliferation
Formation of in situ carcinoma (ductal carcinoma in situ or lobular carcinoma in situ) or invasive carcinoma
Tumor cells invade surrounding stroma, lymphatics, and blood vessels
Expression of hormone receptors (ER, PR) and HER2 receptor influences growth and treatment response
Metastasis commonly occurs to axillary lymph nodes, bone, lung, liver, and brain