USMLE Guide: Breast Cancer

Introduction

Breast cancer is a common malignancy affecting women worldwide. This USMLE guide provides an overview of breast cancer, including its epidemiology, risk factors, clinical presentation, diagnosis, and management.

Epidemiology

• Breast cancer is the most common cancer in women globally.
• Incidence increases with age, with the majority of cases occurring after the age of 50.
• It is more common in developed countries compared to developing nations.

Risk Factors

• Gender: Females are at a higher risk compared to males.
• Age: Advancing age is a significant risk factor.
• Family history: First-degree relatives with breast cancer increase the risk.
• BRCA1 and BRCA2 mutations: Inherited gene mutations increase the risk substantially.
• Personal history: Previous breast cancer or certain benign breast conditions increase the risk.
• Hormonal factors: Early menarche, late menopause, and hormone replacement therapy increase the risk.
• Reproductive factors: Nulliparity, late age at first childbirth, and not breastfeeding increase the risk.
• Alcohol consumption: Increased alcohol intake is associated with a higher risk.
• Obesity: Being overweight or obese increases the risk.

Clinical Presentation

• Breast lump: Most common presenting symptom, usually painless.
• Breast pain: Non-specific symptom, not usually associated with breast cancer.
• Nipple changes: Nipple retraction, discharge, or erosion.
• Skin changes: Dimpling, erythema, peau d'orange appearance.
• Axillary lymphadenopathy: Enlarged lymph nodes in the axilla.

Diagnosis

• Mammography: Screening tool of choice, detects microcalcifications and masses.
• Ultrasound: Used to evaluate breast masses and distinguish between solid and cystic lesions.
• Fine-needle aspiration (FNA): Performed to obtain cytological samples for diagnosis.
• Core needle biopsy: Preferred method for histological diagnosis.
• Imaging: MRI or CT scan may be used for staging purposes.

Staging

Breast cancer staging is based on the TNM system:

• T: Tumor size and invasion.
• N: Lymph node involvement.
• M: Metastasis to distant organs.

Management

• Surgery: Breast-conserving surgery (lumpectomy) or mastectomy.
• Radiation therapy: Adjuvant therapy to reduce local recurrence after surgery.
• Chemotherapy: Systemic treatment for invasive breast cancer.
• Hormonal therapy: Used in hormone receptor-positive breast cancer.
• Targeted therapy: HER2-directed therapy for HER2-positive breast cancer.
• Immunotherapy: Investigational approach in certain cases.

Prognosis

• Prognosis depends on various factors, including tumor stage, grade, and hormone receptor status.
• Five-year survival rates are higher for localized breast cancer compared to metastatic disease.
• Early detection through screening programs improves prognosis.

Conclusion

Breast cancer is a significant health concern affecting women worldwide. Understanding its epidemiology, risk factors, clinical presentation, diagnosis, and management is crucial for physicians preparing for the USMLE. Early detection and appropriate treatment can greatly impact patient outcomes.