USMLE Step 3 Subject Review – Breast Cancer

Breast Cancer is an important topic to understand for the USMLE Step 3, ABIM, and on other medical exams where internal medicine is a major focus. The following is an excerpt out of Cracking the USMLE Step 3. 

• Risk factors include:
  • Age (i.e., greater than 50)
  • Female
  • Family history
  • BRCA 1, 2
  • Obesity
  • Highfat diet
  • Early menarche
  • Late menopause
  • Nulliparity
  • HRT
  • Previous history of breast cancer
• Signs and symptoms include:
  • Most commonly presents as a firm mass in the upper outer quadrant of the breast
  • Nipple or skin retraction
  • Bloody nipple discharge
  • Palpable axillary lymph nodes
  • Back pain
    • If metastasizes, usually does so to the bone
• Different types:
  • Ductal carcinoma in situ (DCIS)
    • More common than LCIS
    • Usually affects one breast and does not increase contralateral breast cancer risk
  • Lobular carcinoma in situ (LCIS)
    • Increases risk for contralateral breast cancer
• Diagnose with FNA and mammogram followed by core needle biopsy if suspicious
• Need to evaluate spread of breast cancer with sentinel lymph node biopsy
  • Also check estrogen and progesterone receptor status
  • Also check Herceptin2/Neu receptor status
    • If positive for both estrogen receptor and Her2/Neu, then better prognosis
      • Can treat with tamoxifen or other selective estrogen receptor modulators (SERMS)
      • Can also treat with herceptin, an antibody that can bind to the Her2/Neu receptor causing cytotoxicity (i.e., type II hypersensitivity reaction)
• Surgical options
  • Consider simple lumpectomy:
    • If no lymph node spread
    • Her2/Neu positive
    • Tumor less than 2 cm especially in large breasts
  • Consider simple mastectomy:
    • If no lymph node spread
    • If patient has small breasts
  • Consider modified radical mastectomy:
    • With any evidence of lymph node spread
    • More popular than radical mastectomies which are no longer common
• If distant spread (i.e., stage IV), surgery is not indicated
  • Administer systemic chemotherapy
• Paget’s Disease of the Breast
  • Noninvasive intraepithelial adenocarcinoma
  • Eczematous lesion around the nipple
  • Diagnose with core needle biopsy
  • Treatment requires local surgical excision
• Screening for breast cancer involves routine mammograms