Types of Breast Cancer

Breast Cancer In Situ

In situ literally means “in the same place” or that the cancer has not invaded into the surrounding tissue or spread to other parts of the body. There are two types of breast cancer in situ, and they describe where the cancer is located.

The most common type of breast cancer in situ occurs in the lining of ductal tissue, which carries milk from lobules to the nipple. This type of breast cancer is known as Ductal Carcinoma in situ or DCIS. The other type of breast cancer in situ is in lobular tissue, which produces the milk that is carried within ducts, and is called Lobular Carcinoma in situ or LCIS. Breast cancer in situ typically shows “microcalcifications”, making it easier to distinguish on mammogram. It is classified as Stage 0; however, DCIS and LCIS have very different risks and when diagnosed alone, are treated quite differently. It is important to note that both can be diagnosed within the same tumor, as some cancers are composed of many different cell types.

Since the early 1990’s, mammography has been used routinely for breast cancer screening. In turn, there was a drastic increase in the number of Stage 0, or breast cancer in situ at diagnosis. However, the rates of invasive cancer have remained essentially constant in postmenopausal women, despite the increased use of mammography.1

There are several treatment options for Stage 0 breast cancer. One option is “lumpectomy” or partial mastectomy followed by radiation therapy which defines Breast Conserving Therapy (BCT). This is most often the case for DCIS, since DCIS is a precursor to Invasive Ductal Carcinoma. On the other hand, LCIS is not a precursor to Invasive Lobular Carcinoma, but a marker of increased risk for developing breast cancer in either breast. Treatment adjuncts include hormonal therapy with tamoxifen or raloxifene, which bind hormonal receptors and decrease the risk of recurrence in selective patients.2 Some patients even choose to have a mastectomy on the side with cancer. Others opt for a therapeutic mastectomy on the cancer side with prophylactic or preventative mastectomy on the side without cancer. This is typically for those with a strong family history of breast cancer, or those that are positive for BRCA 1 or 2, who wish to decrease their lifetime risk of developing breast cancer. Diagnosis at a young age, positive genetic markers and having more than one first degree relative with breast cancer is often associated with the decision to proceed with mastectomy. Some even choose to have a prophylactic bilateral mastectomy without evidence of breast cancer if they have a very strong family history of breast cancer, with positive genetic markers. 3

Invasive Breast Cancer

Invasive breast cancers start in ductal or lobular tissue. These cancer cells continue to divide and as the tumor grows, it invades through the outermost layer of cells and into surrounding tissue. At that point, the cancer cells can spread into lymphatic tissue or directly into the bloodstream on occasion, depending on the location within the breast. Most often, the cancer cells are filtered by the lymphatic system and spread to lymph nodes prior to entering the bloodstream. Once in the lymphatic system, the cancer can spread to other areas of the body, as the lymphatic fluid ultimately drains into the bloodstream. Depending on the size of an invasive tumor, the number and location of lymph nodes it has spread to and whether or not it has spread to other areas of the body, the cancer Stage can range from I to IV.

Cancer also has a grading system that is part of the staging system. The grade of a cancer describes how differentiated it is, or how much the cells have gone from looking like a normal cell to a very abnormal cell. A “well-differentiated” cancer is better than a “poorly-differentiated” cancer, as the latter has become so abnormal, it “doesn’t even look like itself.” The higher the grade, the more aggressive a cancer is and it needs to be treated as such.

Inflammatory Breast Cancer

Inflammatory breast cancer (IBC) is a more rare type of breast cancer, making up only approximately 1-5% of all cases. It has symptoms that are very different than the other kinds of breast cancer, often causing it to be misdiagnosed initially. Symptoms are redness, warmth and swelling of the breast, skin dimpling, nipple inversion and pain. This is often thought to be infection and is treated as such. Unfortunately, IBC is more aggressive than other kinds of breast cancer and while being treated as an infection, can spread to lymph nodes or other parts of the body before being correctly diagnosed. Thus, if what appears to be infection is not healing as it should with appropriate antibiotics, see your doctor immediately.

Hormone Receptor Status

Tissue specimens that are being examined for breast cancer are often tested for the presence and prevalence of hormone receptors, such as estrogen and progesterone. If a cancer does express estrogen or progesterone receptors, they are considered “receptor-positive”, and then a percentage is assigned from 0-100% signifying how weakly or strongly-positive they are. Medications such as tamoxifen or raloxifene, selectively block estrogen receptors that are expressed on these breast cancer cells and may be taken by patients that have receptor-positive cancers to decrease their long-term risk of breast cancer recurrence by as much as 50%. Another class of medicines called aromatase inhibitors, stop the production of estrogen in postmenopausal women and can also lower the risk of breast cancer recurrence in these patients if they have receptor-positive tumors.5

There is a protein-receptor complex that is found on the surface of some breast cancer cells, called Her-2/neu. If the gene that makes this complex is present, it indicates that the cancer is aggressive, making it a negative prognostic factor. However, a medication is available that binds this receptor and prevents the production of Her-2, effectively decreasing the risk of recurrence in patients that are “Her2-positive”.

A very poor prognosis is given when a patient has a cancer that is so-called “triple-negative.” This means that their cancer is negative for estrogen, progesterone and Her2 receptors making it very difficult to treat, as there is no receptor to target with the medications listed above.


1 Li, C. I., Daling, J. R., & Malone, K. E. (2005). Age-Specific Incidence Rates of In situ Breast Carcinomas by Histologic Type, 1980 to 2001 . Cancer Epidemiology, Biomarkers & Prevention , 1008-1011.

2 Vogel, V. G., Constantino, J. P., Wickerham, D. L., & etal. (2010). Carcinoma In Situ Outcomes in National Surgical Adjuvant Breast and Bowel Project Breast Cancer Chemoprevention Trials. Journal of the National Cancer Institute , 181-186.

3 Hoover, D. J., Paragi, P. R., Santoro, E., et al. (2010). Prophylactic Mastectomy in High Risk Patients: A Practice-Based Review of the Indications. Do We Follow Guidelines? Breast Diseases , 19-27.

4 Davoli, A., Hocevar, B., & Brown, T. (2010). Progression and treatment of HER2-positive breast cancer. Cancer, Chemotherapy and Pharmacology , 611-623.

5 Forbes, J., Cuzick, J., Buzdar, A., et al. (2008). Effect of anastrozole and tamoxifen as adjuvant treatment for early-stage breast cancer: 100-month analysis of the ATAC trial. Lancet Oncology , 45-53.

This article was originally published on July 27,2012 and last revision and update of it was 9/2/2015.