Breast Cancer


Most commonly diagnosed cancer (CA) in women and the second most common cause of CA death for U.S. women. Females have a ~2.6% or 1 in 39 chance of dying from breast cancer (BC) in the United States.


  • Malignant neoplasm of cells native to the breast—epithelial, glandular, or stroma
  • Types: ductal carcinoma in situ (DCIS), infiltrating ductal carcinoma, infiltrating lobular carcinoma, Paget disease, phyllodes tumor, inflammatory BC, angiosarcoma
  • Molecular subtypes: luminal A (HR+/HER2−), triple negative (HR−/HER2−), luminal B (HR+/HER2+), HER2-enriched (HR−/HER2+)


Female DCIS: 49,290; invasive BC: 281,550 in 2021; BC have increased by 0.5% per year.

3.8 million BC survivors in the United States (1).

Etiology and Pathophysiology

  • Genes such as BRCA1 and BRCA2 function as tumor suppressor genes, and mutation leads to cell cycle progression and limitations in DNA repair.
  • Mutations in estrogen/progesterone induce cyclin D1 and c-Myc expression, leading to cell cycle progression.
  • Additional tumors (33%) may cross talk with estrogen receptors and epidermal growth factors receptors (EGFRs), leading to similar abnormal cellular replication.


  • Criteria for additional risk evaluation/gene testing in affected BC individual
    • BC at age ≤50 years
    • BC at any age and
      • ≥1 family member with BC ≤50 years of age or ovarian/fallopian tube/primary peritoneal CA any age
      • ≥2 family members with BC or pancreatic CA any age
      • Population at increased risk (e.g., Ashkenazi Jewish descent with BC or ovarian CA at any age)
    • Triple-negative BC (ER−, PR−, HER2−)
    • Two BC primaries, ovarian/fallopian tube/primary peritoneal CA
    • ≥1 family member with BC and CA of thyroid, adrenal cortex, endometrium, pancreas, central nervous system (CNS), diffuse gastric, aggressive prostate (Gleason score of >7), leukemia, lymphoma, sarcoma, dermatologic manifestations, and/or macrocephaly, gastrointestinal (GI) hamartomas
    • Male BC
  • Criteria for additional risk evaluation/gene testing in unaffected BC individual
    • First- or second-degree relative with BC ≤45 years of age
    • ≥2 breast primaries in one individual
    • ≥1 ovarian/fallopian tube/primary peritoneal CA from same side of family
    • ≥2 with breast primaries on same side of family
    • ≥1 family member with BC and CA of thyroid, adrenal cortex, endometrium, pancreas, CNS, diffuse gastric, aggressive prostate, leukemia, lymphoma, sarcoma, dermatologic manifestations, and/or macrocephaly, GI hamartomas
    • Ashkenazi Jew with BC/ovarian CA at any age
    • Male BC
  • BRCA1 and BRCA2 are inherited in an autosomal fashion and account for 5–10% of female and 5–20% male CAs; 15–20% familial BCs
  • Syndromes associated with BC: Cowden syndrome (PTEN), Li-Fraumeni syndrome (TP53), ataxia-telangiectasia (ATM), and Peutz-Jeghers (STK11)

Risk Factors

  • National Cancer Institute Breast Cancer Risk Assessment Tool:
  • Hormone replacement therapy (combination estrogen-progesterone and estrogen only agents [but not vaginal estrogen]) during perimenopause increases BC risk for 10 years after medication is discontinued.
  • Age >65 years, biopsy confirmed atypical hyperplasia, DCIS, lobular carcinoma in situ (LCIS)
  • BRCA mutation, Ashkenazi Jewish descent
  • Personal history of BC <40 years
  • First-degree relatives diagnosed at an early age
  • Postmenopausal
  • History of radiation
  • Increased alcohol use
  • Diethylstilbestrol exposure
  • Early menarche (<12 years old), late menopause (>55 years old), first pregnancy at >30 years old
  • Proliferative breast disease without atypia (fibroadenoma or ductal hyperplasia)
  • Dense breasts (>50%)
  • Nulliparous/no history of full-term pregnancy/no history of breastfeeding
  • Obesity
  • History of endometrial or ovarian CA
  • Hormone replacement therapy

General Prevention

  • Maintain healthy weight—obesity increases BC risk.
  • Limit alcohol use—≤1 serving of alcohol per day is recommended.
  • High serum 25-OH vitamin D levels correlate with lower BC risk; consider vitamin D supplementation.
  • Medication: The U.S. Preventive Services Task Force (USPSTF) recommends that clinicians offer to prescribe risk-reducing medications, such as tamoxifen, raloxifene, or aromatase inhibitors (AIs), to women who have a >3% risk for BC and low risk for adverse medication effects (B recommendation).
  • Breast self-exams (BSEs): no longer recommended.
  • Clinical breast exam (CBE): USPSTF: insufficient evidence to assess clinical benefits and harms; American Cancer Society (ACS): no clear benefit
  • Mammography:
    • USPSTF: Women should undergo biennial mammogram starting at age 50 years until age 74 years
    • ACS: Women annual mammograms starting at age 45 to 54 years and then women >55 years old biennial mammograms or yearly screening if desired (1).

Commonly Associated Conditions

  • Li-Fraumeni and Cowden disease
  • History of atypical ductal hyperplasia (ADH), atypical lobular hyperplasia (ALH), and LCIS
  • Obesity

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