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Breast Cancer for ABIM

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Breast Cancer for the American Board of Internal Medicine Exam
Definition and Classification
  • Definition
    • Breast cancer is a malignant tumor arising from breast tissue, primarily from the ducts (ductal carcinoma) or lobules (lobular carcinoma).
    • Most common histologic types include:
    • Invasive Ductal Carcinoma (IDC): Accounts for approximately 70-80% of breast cancers.
    • Invasive Lobular Carcinoma (ILC): Represents 10-15% of cases.
  • Classification by Receptor Status
    • Tumors are classified based on expression of hormone receptors and HER2 status:
    • Hormone Receptor-Positive (ER+ or PR+): Responds to hormonal therapy, accounting for about 70% of breast cancers.
    • HER2-Positive: Overexpresses the HER2 receptor, associated with more aggressive behavior; treated with HER2-targeted therapies.
    • Triple-Negative Breast Cancer (TNBC): Lacks ER, PR, and HER2 expression; more aggressive and associated with a poorer prognosis, often treated with chemotherapy.
Epidemiology
  • Incidence and Mortality
    • Breast cancer is the most common cancer and the second leading cause of cancer death in women.
    • The incidence increases with age, particularly after 50, and is higher in developed countries.
  • Risk Factors
    • Non-Modifiable: Female gender, increasing age, family history of breast or ovarian cancer, BRCA1/2 mutations, and dense breast tissue.
    • Modifiable: Alcohol consumption, obesity, sedentary lifestyle, late age at first pregnancy, nulliparity, and use of hormone replacement therapy (HRT) post-menopause.
Pathophysiology
  • Genetic Mutations
    • BRCA1 and BRCA2: Germline mutations linked to high breast and ovarian cancer risk; associated with early-onset breast cancer and TNBC.
    • p53, PTEN, and CHEK2: Additional mutations associated with sporadic breast cancer.
  • Hormonal Influence
    • Estrogen and progesterone play a key role in stimulating breast epithelial cell proliferation, particularly in hormone receptor-positive cancers.
Clinical Manifestations
  • Palpable Mass
    • Most common presenting symptom is a painless lump, often firm with irregular borders.
    • May be fixed to surrounding tissues if advanced.
  • Skin and Nipple Changes
    • Skin dimpling, nipple retraction, or discharge (especially bloody) can be signs of advanced disease.
    • Inflammatory breast cancer presents as erythema, edema, and peau d’orange (skin thickening).
  • Axillary Lymphadenopathy
    • Enlarged axillary lymph nodes may indicate metastatic spread.
breast cancer breast changes
Screening
  • Guidelines
    • Women aged 40-74 are recommended to have biennial mammograms per US Preventive Services Task Force (USPSTF) recommendations.
    • High-risk women (e.g., BRCA mutations) may start annual mammography and MRI screening as early as 25-30 years of age.
  • Screening Modalities
    • Mammography: First-line screening tool, with 2D and 3D (digital breast tomosynthesis) options.
    • Breast MRI: Used as an adjunct for high-risk women or those with dense breasts.
Diagnosis
  • Physical Examination
    • Clinical breast exam includes palpation of breast tissue and lymph nodes to assess for masses or skin/nipple changes.
  • Imaging
    • Diagnostic Mammogram: Provides more detailed imaging for symptomatic patients or abnormal screening results.
    • Ultrasound: Used to differentiate cystic from solid masses and evaluate axillary lymph nodes.
  • Tissue Sampling
    • Core Needle Biopsy: Preferred for definitive diagnosis, providing histopathologic and receptor status information.
    • Fine-Needle Aspiration (FNA): May be used for palpable masses but provides less tissue for diagnosis.
Staging
  • TNM System
    • Tumor staging considers tumor size (T), lymph node involvement (N), and presence of metastasis (M).
    • Staging ranges from Stage 0 (in situ) to Stage IV (distant metastasis).
  • Prognostic Factors
    • Tumor grade, hormone receptor status, HER2 status, and lymph node involvement influence prognosis and treatment options.
Treatment
  • Surgical Options
    • Lumpectomy (Breast-Conserving Surgery): Removal of the tumor with a margin of normal tissue, often followed by radiation.
    • Mastectomy: Complete removal of breast tissue, recommended in larger tumors or multicentric disease.
    • Sentinel Lymph Node Biopsy (SLNB): Evaluates lymph node spread; axillary dissection may be done if positive.
  • Radiation Therapy
    • Indicated after lumpectomy to reduce local recurrence, or in select cases following mastectomy, especially if lymph nodes are positive or tumor size >5 cm.
  • Systemic Therapy
    • Hormonal Therapy: For ER/PR-positive tumors, commonly using selective estrogen receptor modulators (SERMs) like tamoxifen in premenopausal women or aromatase inhibitors in postmenopausal women.
    • Chemotherapy: Often used for high-risk cases, TNBC, or HER2-positive tumors; regimens include anthracyclines, taxanes, and/or platinum agents.
    • HER2-Targeted Therapy: HER2-positive tumors are treated with trastuzumab and other HER2-targeted agents.
  • Immunotherapy
    • Emerging role in TNBC with immune checkpoint inhibitors (e.g., pembrolizumab) in metastatic or high-risk disease.
Follow-Up and Surveillance
  • Post-Treatment Surveillance
    • Regular clinical exams and annual mammograms for early detection of recurrence.
    • High-risk patients may require imaging beyond mammography, such as MRI.
  • Lifestyle Modifications
    • Encouraged to reduce recurrence risk, including maintaining a healthy weight, regular physical activity, limited alcohol intake, and smoking cessation.
Complications
  • Local and Regional Recurrence
    • Higher risk in large tumors, positive margins, or lymph node involvement.
    • Local recurrence is generally managed with surgery and/or radiation.
  • Metastatic Disease
    • Common metastatic sites include bones, lungs, liver, and brain, managed with systemic therapies to prolong survival and manage symptoms.
  • Treatment-Related Complications
    • Surgical: Lymphedema, infection, pain.
    • Radiation: Skin changes, fatigue, rare risk of secondary malignancies.
    • Chemotherapy: Neuropathy, cardiotoxicity (particularly from anthracyclines), and myelosuppression.
Key Points
  • Breast Cancer is the most common cancer in women, with risk factors including age, family history, genetic mutations (BRCA), and lifestyle factors.
  • Classification is based on receptor status (ER, PR, HER2) to guide therapy:
    • ER/PR-positive tumors respond to hormonal therapy.
    • HER2-positive cancers respond to HER2-targeted therapies.
    • Triple-negative breast cancer (TNBC) lacks all three receptors and has limited targeted treatment options.
  • Screening recommendations vary based on age and risk; mammography is the primary modality, with MRI used for high-risk populations.
  • Diagnosis involves clinical exam, imaging (mammography, ultrasound, MRI), and biopsy for histologic evaluation.
  • Staging uses the TNM system and incorporates prognostic factors such as tumor grade, receptor status, and lymph node involvement.
  • Treatment:
    • Surgery (lumpectomy or mastectomy) with or without radiation, based on tumor size and spread.
    • Systemic therapy includes hormonal therapy for ER/PR-positive tumors, chemotherapy for high-risk cases or TNBC, and HER2-targeted agents for HER2-positive disease.
  • Follow-Up:
    • Surveillance includes regular physical exams and annual mammograms.
    • Lifestyle changes, such as healthy diet, exercise, and avoiding alcohol, are recommended to reduce recurrence risk.
  • Complications include local recurrence, metastasis, and treatment-related side effects like lymphedema and cardiotoxicity from chemotherapy.

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