A friend of mine has HER2-positive breast cancer. Can you tell me what this means?

HER2-positive breast cancer is a breast cancer that tests positive for a protein called human epidermal growth factor receptor 2 (HER2). This protein promotes the growth of cancer cells.

In about 1 of every 5 breast cancers, the cancer cells have extra copies of the gene that makes the HER2 protein. HER2-positive breast cancers tend to be more aggressive than other types of breast cancer.

Treatments that specifically target HER2 are very effective. These treatments are so effective that the prognosis for HER2-positive breast cancer is actually quite good.

Certain standard chemotherapy drugs also can be effective in treating HER2-positive breast cancers, although these drugs don't specifically target the HER2 protein.

Experts recommend that every invasive breast cancer be tested for the presence of HER2 because the results significantly impact treatment recommendations and decisions. HER2 testing is not done routinely for ductal carcinoma in situ, except as part of a clinical trial.

Whenever breast cancer recurs or spreads, the cancer cells should be retested for HER2 as well as for hormone receptor status, as these can change from the original diagnosis.

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April 09, 2024 See more Expert Answers

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  8. BRCA gene test
  9. Breast cancer
  10. Breast cancer chemoprevention: Drugs that reduce risk
  11. Breast Cancer Education Tool
  12. Breast cancer prevention: How to reduce your risk
  13. Breast cancer risk assessment
  14. Breast cancer staging
  15. Breast cancer supportive therapy and survivorship
  16. Breast cancer surgery
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  19. Breast lump or breast changes: Early evaluation is essential
  20. Breast MRI
  21. Breast reconstruction with flap surgery
  22. Breast reconstruction with implants
  23. Breast self-exam for breast awareness
  24. Cancer blood tests: Lab tests used in cancer diagnosis
  25. Cancer treatment
  26. Cancer treatment myths: Any truth to these common beliefs?
  27. Chemo targets
  28. Chemotherapy
  29. Chemotherapy and hair loss: What to expect during treatment
  30. Chemotherapy and sex: Is sexual activity OK during treatment?
  31. Chemotherapy for breast cancer
  32. Chemotherapy nausea and vomiting: Prevention is best defense
  33. Chest X-rays
  34. Common questions about breast cancer treatment
  35. Complete blood count (CBC)
  36. Coping with pain after breast surgery
  37. COVID-19 vaccine: Should I reschedule my mammogram?
  38. CT scan
  39. Dense breast tissue: What it means to have dense breasts
  40. Does soy really affect breast cancer risk?
  41. Doppler ultrasound: What is it used for?
  42. Dragon Boats and Breast Cancer
  43. Genetic Testing for Breast Cancer
  44. Genetic testing for breast cancer: Psychological and social impact
  45. Hormone therapy for breast cancer
  46. Infographic: Breast Cancer Risk
  47. Lumpectomy
  48. Magic mouthwash
  49. Mammogram
  50. Mammogram for breast cancer — What to expect
  51. Mammogram guidelines: What are they?
  52. Mastectomy
  53. Molecular breast imaging
  54. Monoclonal antibody medicines for cancer: How they work
  55. Mouth sores caused by cancer treatment: How to cope
  56. MRI
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  58. PALS (Pets Are Loving Support)
  59. Pink Sisters
  60. Positron emission tomography scan
  61. Precision medicine for breast cancer
  62. Pressurized intraperitoneal aerosol chemotherapy (PIPAC)
  63. Radiation therapy
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  65. Seeing inside the heart with MRI
  66. Sentinel node biopsy
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  68. Support groups: Make connections, get help
  69. The Long Race Beating Cancer
  70. Thyroid guard: Do I need one during a mammogram?
  71. Ultrasound
  72. Weight Loss After Breast Cancer
  73. What is breast cancer? An expert explains
  74. X-ray