Breast Cancer

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Types and Grades of Breast Cancer

To understand how your breast cancer is likely to behave and which treatments are most likely to stop it, your doctors will determine several traits of your cancer at the time of your diagnosis or soon after. These include:

Types of Breast Cancer

Breast cancers fall into these two main categories:

  • In situ breast cancers, also called noninvasive breast cancers: These are cancers confined to breast ducts (milk tubes) and lobules (milk-producing glands).
  • Invasive breast cancers, also called infiltrating breast cancers: These cancers can start in the ducts or lobules, but then they spread into surrounding breast tissue. Invasive cancers may eventually become metastatic, meaning they find their way to other organs, like the bones, lungs, liver, and brain.

The American Cancer Society estimated that 207,090 new cases of invasive breast cancer would be diagnosed among women and another 54,010 cases of in situ breast cancer would be diagnosed in 2010.

In Situ Breast Cancers

There are two types of in situ breast cancers.

  • Ductal carcinoma in situ (DCIS): Ductal carcinoma in situ is a condition in which abnormal cells are confined to the milk ducts in the breast. This is the most common type of noninvasive breast cancer. DCIS is considered early-stage cancer. Many women diagnosed at this early stage can be cured by removing the tissue that contains the tumor. Left untreated, DCIS can become invasive. DCIS typically has no physical signs or symptoms. It is usually detected by a screening mammogram.
  • Lobular carcinoma in situ (LCIS): Cancer that begins in the lobes or lobules of the breast is called lobular carcinoma. It is more likely than other types of breast cancer to be found in both breasts. There is some controversy among oncologists about exactly how to think about LCIS. The question is whether LCIS is a precancerous condition—that is, it will turn into invasive cancer at its current site if it’s not treated—or whether it is a risk factor for cancer—that is, it indicates greater risk for cancer, either at its current site or elsewhere. LCIS has features of both a precancerous condition and a cancer risk factor. LCIS is sometimes called lobular neoplasia.

Invasive Breast Cancer

The following are the most common types of invasive breast cancer.

  • Invasive ductal carcinoma (IDC): About 80 percent of invasive breast cancers are invasive ductal carcinomas, also called infiltrating ductal carcinomas. IDC begins in a duct in the breast and breaks through into the surrounding fatty tissue of the breast. From there, IDC can metastasize (spread) to other parts of the body through the bloodstream or lymphatic system.
  • Invasive lobular carcinoma (ILC): Invasive lobular carcinoma is the second most common type of invasive breast cancer. ILC starts in the lobules and, like IDC, can spread to other parts of the body. It is also called infiltrating lobular carcinoma.
  • Inflammatory breast cancer (IBC): Only about 1 to 3 percent of all women diagnosed with breast cancer have IBC. This rare cancer is invasive and may begin in either the ducts or the lobules. It is very aggressive and progresses rapidly, making the breast red, swollen and warm to the touch. The surface of the breast may look pitted like the skin of an orange because the cancer cells block lymph vessels in the skin. Typically there is no single lump in the breast. In its early stages, IBC can be mistaken for infection because the symptoms are similar. However, most infections will respond to antibiotics, but inflammatory breast cancer will not. IBC occurs more frequently and at a younger age in African Americans than in European Americans. It can occur in men, too, usually at an older age.

Breast Cancer Grades

The grade of a breast cancer tumor refers to how closely the cancer resembles normal breast cells. The grading system is used for invasive cancers only, not for in situ cancers. In general, a lower grade number indicates a slower-growing cancer that is less likely to spread, while a higher number indicates a faster-growing cancer that is more likely to spread.

Breast cancer grade is determined as part of a biopsy. There are three grades.

  • Grade 1 (well differentiated): These cancers have relatively normal-looking cells that do not appear to be growing rapidly and are arranged in small tubules.
  • Grade 2 (moderately differentiated): These cancers have cells that are somewhat abnormal.
  • Grade 3 (poorly differentiated): These cancers have cells that look abnormal and tend to grow and spread more aggressively. 

The grade of a breast cancer is different from the stage. Stage is based on where the cancer has spread. Also read about breast cancer stages.

Other Factors

Your care team will try to determine other traits of your breast cancer when they check the sample of tissue removed during your biopsy or a sample taken when your entire tumor is removed surgically. Specifically, they will be looking for the following two traits:

  • Hormone-receptor status: Most women with breast cancer have hormone-receptor positive (HR+) disease. This means their cancer cells have receptors where hormones, like estrogen and progesterone, can attach. If your cancer is HR+, this helps doctors predict that your cancer will respond to hormonal therapy. 
  • HER2 status: Some women with breast cancer have HER2-positive disease. This means their cancer cells make too much of a protein called HER2/neu. If your cancer is HER2 positive, this helps doctors predict that your cancer will respond to certain targeted biological therapies.