Breast cancer is “invasive” when it has spread from the part of the breast where it began into surrounding breast tissue. It may also spread via the blood or lymph system to distant parts of the body.

The main types are invasive ductal carcinoma and invasive lobular carcinoma. There are also less common forms, including tubular carcinoma, papillary carcinoma, or medullary carcinoma.

This article looks at the types and symptoms of invasive breast cancer. It also discusses the process of diagnosing and treating invasive breast cancer and a person’s potential outlook.

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The National Cancer Institute defines invasive breast cancer as cancer that has spread from the part of the breast it began in, such as the milk ducts or milk glands, to surrounding breast tissue.

Invasive breast cancer may spread to other areas of the body through blood or the lymph system.

People may also refer to invasive breast cancer as infiltrating breast cancer.

According to the American Cancer Society (ACS), most types of breast cancer are invasive. Invasive ductal carcinoma (IDC) and invasive lobular carcinoma (ILC) are the two main types of invasive breast cancer.

IDC is the most common form of breast cancer and accounts for around 8 in 10 cases of invasive breast cancer.

It begins in the cells that make up the lining of the milk ducts. The milk ducts are small tubes that transport milk from the breast lobules to the nipple. Cancerous cells may spread from the milk ducts into surrounding breast tissue.

Once IDC begins growing in the breast tissue, it may travel through the blood or lymph systems to other body areas.

Symptoms

Symptoms of IDC may include:

  • a lump in the breast or underarm area
  • thickening or dimpling of breast skin
  • skin color changes
  • change of breast shape
  • persistent breast pain
  • a retracted nipple
  • unusual nipple discharge
  • scaly or flaky skin, or a sore, on the breast or nipple

ILC is less common than IDC and accounts for around 1 in 10 types of invasive breast cancer.

It begins in the lobules, the glands in the breast that produce milk. Cancer may then spread to surrounding breast tissue and other areas of the body.

ILC is more likely to occur in both breasts than other types of invasive breast cancer. At the time of diagnosis, 1 in 5 people may have ILC in both breasts.

Symptoms

Symptoms of ILC may include:

  • thickening of the skin of the breast, or changes in texture
  • swelling or fullness of the breast
  • an inward-turning nipple

The ACS notes that inflammatory breast cancer (IBC) is another type of invasive breast cancer. However, this form is rare. Around 1–5% of all types of breast cancer may be IBC.

In IBC, cancer cells cause a blockage in lymph vessels in the skin of the breast, which gives the breast an inflamed appearance.

Most cases of IBC are IDC, meaning the cancer begins in the lining of the milk ducts.

IBC symptoms

IBC may have different symptoms from other types of invasive breast cancer. It usually does not cause a lump and may be difficult to detect on a mammogram.

Symptoms of IBC may develop quickly over 3–6 months and include:

  • swelling of the breast, making it seem larger than usual
  • changes in the color of the skin, usually over more than one-third of the breast
  • thickening and pitting of the breast skin, similar to the texture of orange peel
  • an inward-facing nipple
  • one breast feeling heavier and warmer than the other
  • the breast feeling tender, painful, or itchy
  • swollen lymph nodes near the collarbone or under the arms

Other types

Other types of invasive breast cancer that make up less than 5% of all breast cancer types include:

Generally, healthcare professionals will treat these types of invasive breast cancer in the same way they treat IDC.

To diagnose invasive breast cancer, doctors may carry out the following:

ILC may be more difficult to detect through physical examinations and mammograms than IDC. ILC is also more likely to occur in both breasts rather than one.

After diagnosing invasive breast cancer, doctors may carry out tests on biopsy samples to determine the type of cancer a person has. These tests may look for:

  • estrogen and progesterone receptors to see if the cancer will respond to hormone therapies
  • the amount of HER2 protein in cancer cells
  • how much the cells resemble typical or atypical cells, to work out the tumor grade

They may also use a PET, CT, or bone scan to determine whether cancer has spread to other body areas.

The results of these tests will help determine the best course of treatment.

Treatment for invasive breast cancer may depend on the stage, type, and location of the cancer, the tumor grade, and the person’s overall health.

It may include:

  • Surgery: Tumor removal may involve a lumpectomy to remove part of the breast or a mastectomy to remove the whole breast.
  • Chemotherapy: Chemotherapy targets the whole body to help destroy cancer cells and reduce the risk of the cancer recurring in another area of the body.
  • Radiation therapy: People may have radiation therapy after surgery to remove any remaining cancer cells.
  • Hormone therapy: If breast cancer is hormone receptor-positive, hormonal medications may help treat it.
  • Targeted therapy: Targeted therapy drugs help activate the immune system to better destroy cancer cells.

People may also want to consider taking part in a clinical trial to receive new treatment options.

Early stage breast cancer may have a higher survival rate than advanced stage cancers. With treatment, early stage breast cancer that has not spread to distant areas of the body is curable in around 70–80% of cases.

A relative survival rate helps give an idea of how long a person with a particular condition will live after receiving a diagnosis compared with those without the condition.

For example, if the 5-year relative survival rate is 70%, a person with the condition is 70% as likely to live for 5 years as someone without the condition.

It is important to remember that these figures are estimates. A person can consult a healthcare professional about how their condition may affect them.

According to the ACS, the 5-year relative survival rate for invasive breast cancer that has not spread outside the breast is 99%.

For all breast cancer types, the 5-year relative survival rates are 86% for breast cancer that has spread to the nearby lymph nodes and structures and 29% for breast cancer that has spread to distant parts of the body.

IBC grows more quickly than other types of breast cancer and may be more likely to recur after treatment. The 5-year relative survival rates for IBC diagnoses between 2011 and 2017 were:

Stage5-year relative survival rate
Regional54%
Distant19%
All stages combined40%

Invasive breast cancer is cancer that has spread from the milk ducts or glands into surrounding breast tissue. Invasive breast cancer that has not spread outside the breast has a high survival rate.

If people notice any unusual breast changes, it is best to contact a doctor for a checkup as soon as possible. Many breast changes are noncancerous and occur due to other conditions. However, it is important to find out the underlying cause.