Multifocal breast cancer occurs when there are two or more tumors in the same breast. All of the tumors begin in one original tumor. The tumors are also all in the same quadrant — or section — of the breast.

Multicentric breast cancer is a similar type of cancer. More than one tumor develops, but in different quadrants of the breast.

Anywhere from 6 to 60 percent of breast tumors are multifocal or multicentric, depending on how they’re defined and diagnosed.

Multifocal tumors can be noninvasive or invasive.

  • Noninvasive cancers stay in the milk ducts or milk-producing glands (lobules) of the breast.
  • Invasive cancers can grow into other parts of the breast and spread to other organs.

Keep reading to learn more about the types of breast cancer that may develop with multifocal breast cancer, what treatment may consist of, and more.

There are several types of breast cancer, and they’re based on the type of cells the cancer grows from.

Most breast cancers are carcinomas. This means that they start in epithelial cells that line the breasts. Adenocarcinoma is a type of carcinoma that grows from the milk ducts or lobules.

Breast cancer is further categorized into these types:

  • Ductal carcinoma in situ (DCIS) starts inside the milk ducts. It’s called noninvasive because it hasn’t spread outside of these ducts. However, having this cancer can increase your risk for an invasive breast cancer. DCIS is the most common type of noninvasive breast cancer. It makes up 25 percent of all breast cancers diagnosed in the United States.
  • Lobular carcinoma in situ (LCIS) is also noninvasive. The abnormal cells start in the milk-producing glands of the breast. LCIS can increase your risk for getting breast cancer in the future. LCIS is rare, showing up in just 0.5 to 4 percent of all noncancerous breast biopsies.
  • Invasive ductal carcinoma (IDC) is the most common type of breast cancer, accounting for about 80 percent of these cancers. IDC starts in cells that line the milk ducts. It can grow into the rest of the breast, as well as to other parts of the body.
  • Invasive lobular carcinoma (ILC) starts in the lobules and can spread to other parts of the body. About 10 percent of all invasive breast cancers are ILC.
  • Inflammatory breast cancer is a rare form that spreads aggressively. Between 1 and 5 percent of all breast cancers are this type.
  • Paget’s disease of the nipple is a rare cancer that starts in the milk ducts but spreads to the nipple. About 1 to 3 percent of breast cancers are this type.
  • Phyllodes tumors get their name from the leaflike pattern in which the cancer cells grow. These tumors are rare. Most are noncancerous, but malignancy is possible. Phyllodes tumors make up less than 1 percent of all breast cancers.
  • Angiosarcoma starts in cells that line blood or lymph vessels. Less than 0.05 percent of breast cancers are this type.

Doctors use a few different tests to diagnose breast cancer.

These include:

  • Clinical breast exam. Your doctor will feel your breasts and lymph nodes for any lumps or other abnormal changes.
  • Mammogram. This test uses an X-ray to detect changes in the breasts and screen for cancer. The age at which you should start having this test, and its frequency, depends on your breast cancer risk. If you have an abnormal mammogram, your doctor may recommend having one or more of the tests below.
  • Magnetic resonance imaging (MRI). This test uses powerful magnets and radio waves to create detailed pictures of the inside of the breast. It’s more accurate at picking up multifocal breast cancer than mammography and ultrasound.
  • Ultrasound. This test uses sound waves to look for masses or other changes in your breasts.
  • Biopsy. This is the only way for your doctor to know for sure that you have cancer. Your doctor will use a needle to remove a small sample of tissue from your breast. A biopsy may also be taken of the sentinel lymph node — the lymph node where cancer cells are most likely to spread first from the tumor. The sample is sent to a lab, where it’s checked for cancer.

Based on these and other test results, your doctor will stage your cancer. Staging shows how large the cancer is, whether it has spread, and if so, how far. It can help your doctor plan your treatment.

In multifocal cancer, each tumor is measured separately. The disease is staged based on the size of the largest tumor. Some experts say this method isn’t accurate because it doesn’t take into account the total number of tumors in the breast. Still, this is the way multifocal breast cancer is usually staged.

Your treatment will depend on the stage of your cancer. If the cancer is early stage — meaning the tumors are only in one quadrant of your breast — breast-conserving surgery (lumpectomy) is possible. This procedure removes as much of the cancer as possible, while preserving the healthy breast tissue around it.

After surgery, you’ll get radiation to kill any cancer cells that might have been left behind. Chemotherapy is another option after surgery.

Large tumors or cancers that have spread may require mastectomy — surgery to remove the whole breast. Lymph nodes may also be removed during the surgery.

Although breast cancer treatments can improve your survival odds, they can have side effects.

Side effects from breast-conserving surgery include:

  • pain in the breast
  • scarring
  • swelling in the breast or arm (lymphedema)
  • change in the shape of the breast
  • bleeding
  • infection

Radiation side effects include:

  • redness, itching, peeling, and irritation of the skin
  • fatigue
  • swelling in the breast

Multifocal breast cancers are more likely than single tumors to spread to the lymph nodes. However, research shows that 5-year survival rates aren’t any different for multifocal tumors than for single tumors.

Your outlook depends less on how many tumors you have in one breast, and more on the size of your tumors and whether they have spread. Overall, the 5-year survival rate for cancer that is confined to the breast is 99 percent. If the cancer has spread to lymph nodes in the area, the 5-year survival rate is 85 percent.

If you’ve recently been diagnosed with multifocal breast cancer, you might have a lot of questions about everything from your treatment options to how much they’ll cost. Your doctor and the rest of your medical team can be good sources for this information.

You can also find more information and support groups in your area through cancer organizations like these: