Invasive Ductal Breast Cancer (IDC)

Invasive ductal breast cancer (IDC), also known as infiltrating ductal carcinoma, is the most common form of invasive breast cancer and represents 80 percent of breast cancer cases.

The condition begins with abnormal cells forming in the milk ducts of the breast (ductal). These cells then spread into the surrounding fatty breast tissue (invasive). Invasive ductal cancers can spread along the blood and lymphatic channels to other parts of the body. Because of this, treatment of invasive ductal cancers requires surgery to remove the cancer in the breast, as well as some of the underarm lymph nodes to determine the cancer stage.


Patients with IDC may not notice any symptoms. When symptoms are present, they may include:

  • Breast lump
  • Nipple discharge
  • Thickening of the breast skin
  • Rash or redness on the breast
  • Swelling in one breast
  • Dimpling of the nipple or breast skin
  • Rash on the nipple
  • The nipple turning inward
  • Lumps in the underarm
  • Unusual changes in breast or nipple appearance

Causes and Risk Factors

Certain genetic mutations, known as breast cancer genes BRCA1 and BRCA2, are associated with an increased risk of IDC. Other risk factors include:

  • Age
  • A history of benign breast disease
  • A family history of breast cancer
  • First pregnancy after the age of 30
  • Obesity
  • Using combination estrogen-progestin hormone replacement therapy for more than five years after menopause


IDC may be diagnosed during a routine mammogram. If the medical team sees evidence of IDC during the mammogram, a biopsy will be performed. During a biopsy, a sample of the abnormal tissue will be taken using a needle. The medical team may use stereotactic images, such as mammography or ultrasound, to guide the needle to the area of concern. A specialist, known as a pathologist, will examine the tissue sample under a microscope and determine if cancer is present.


Treatment of IDC will depend on the characteristics of the tumor present, including the type, size and spread of the tumor. Treatment options that may be considered for breast cancer include:

  • Radiation therapy. Radiation therapy uses high-energy radiation to kill the cancer cells. The radiation may be directed from outside the body (external) or it may come from an implant placed inside the breast.
  • Chemotherapy. Often prescribed prior to surgery, chemotherapy uses drugs (either as a pill or through an IV) to kill the cancer cells.
  • Hormone therapy. The hormone estrogen has been associated with breast cancer and for some patients hormone therapy may be an option. This method of treatment blocks estrogen from reaching the breast tissue.
  • Surgery. Surgery to remove the affected tissue may include breast-sparing techniques or the removal of the entire breast. A lumpectomy, which removes the affected tissue while preserving as much of the natural breast tissue as possible, is the most conservative option and is generally paired with radiation therapy.

    For some patients, a mastectomy, a procedure that removes all of the breast tissue, may be the best course of treatment. There are different forms of mastectomy surgeries including nipple-sparing and skin-sparing options.

    Removing the lymph nodes in the underarms may also be needed. This can be done as either a sentinel lymph node biopsy or axillary lymph node dissection.