By Marshalee George, Kimlin Tam Ashing

You’ve heard the terms tumor and cancer thrown around. But is there a difference — and if so, what is it? Technically there is a difference, although many people use these terms interchangeably.

A benign tumor or neoplasm is a mass that is generally harmless, as this is an overgrowth of normal tissue. An example would be a freckle or benign mole that grows on the skin, or the raised lumpy tissue that forms over a cut to create scar tissue.

A malignant (cancerous) tumor is bad news, as this is an overgrowth of mutated tissue. A malignant tumor is also called a cancer (or malignant neoplasm). An example would be a mole that undergoes mutations to become a melanoma (a type of skin cancer).

When the term cancer is used, it refers to new malignant growths that have the ability to spread to surrounding tissues and organs. As cancer tissue grows it can begin to infiltrate and replace all the normal tissue which can prevent an organ, for example, from functioning. Cancer sucks the nutrients and blood supply from your body to itself through a process called angiogenesis. Angiogenesis is when new blood vessels are formed from your existing blood vessels that are necessary for cancer growth. The blood vessels carry oxygenated blood and nutrients to the cancer, causing the cancer to grow and eventually spread to other organs (metastasis), and this can lead to death if left untreated.

Understanding angiogenesis is a very important area of research. Some treatments for breast cancer, such as chemotherapy, focus on disrupting the blood supply to the cancer, causing cell death.

In medical terminology, the location of the cancer cells in the body determines what it’s called. So, if the cancer is found in the breast, it’s called breast cancer. There are different types of breast cancer that are defined by the part of the breast where the cancer is found. The different types of breast cancer are as follows:

  • Ductal carcinoma (cancer of the milk ducts): When cancer is found within the milk ducts of the breast, it is called ductal carcinoma. Ductal carcinoma is the most common type of breast cancer. It affects the lining of the milk ducts that carry breast milk from the lobules, where it’s made, to the nipple. If the cancer is limited to the lining of the ducts it is called DCIS (ductal carcinoma in situ). When the cancer breaks out of the milk ducts and starts to infiltrate the rest of the breast, it is considered invasive or infiltrating ductal carcinoma. DCIS and invasive ductal carcinoma are illustrated here.
breast-dcis
Illustration courtesy of the website of the National Cancer Institute (www.cancer.gov)

Ductal carcinoma in situ (DCIS).

breast-invasive
Illustration courtesy of the website of the National Cancer Institute (www.cancer.gov)

Invasive ductal carcinoma.

  • Lobular carcinoma (cancer of the lobules): When cancer is found within the lobules of the breast, where breast milk is produced, it is called lobular carcinoma. If the cancer is limited to a small area in the lobule it is called LCIS (lobular carcinoma in situ). When the cancer breaks out of the lobules, it is considered invasive or infiltrating lobular carcinoma.
  • Inflammatory breast cancer: This is a rare, aggressive form of breast cancer that often invades the lymphatic vessels and skin of the breast. It can be confused with an infection initially, as it will often cause an area of redness and swelling on the breast.
breast-inflammatory
Illustration by Kathryn Born

Inflammatory breast cancer.

  • Phyllodes tumor (cystosarcoma — cancer of the connective tissues): This is an even rarer type of breast cancer that doesn’t usually spread to other areas of the body. There are two main types of phyllodes tumor: benign and malignant. No one knows what causes phyllodes tumors, but they appear to be more common in women with a history of fibroadenomas (benign breast lumps) and in women who are pre-menopausal between the ages of 35 to 50.

Cancer has the unfortunate tendency to not stay put, and when it travels, it brings destruction wherever it goes. When doctors find cancer in the breast, they immediately want to know whether the breast cancer has spread to the lymph nodes, and if so, how far it has spread. If the closest lymph node to the breast is found to have cancer cells, then additional lymph nodes are usually examined to determine if cancer cells are present.

Lobular carcinoma in situ (LCIS), although it sounds like a cancer because it includes the term carcinoma, is not cancer. LCIS is a tumor that grows in the milk-producing lobules of the breast and remains inside the lobule — that is, it does not spread to other tissues. Unfortunately, having LCIS may increase your risk of developing invasive breast cancer in the future. In some people there may be a small area of malignant cancer hidden within an area of LCIS, which is why it has been recommended that LCIS be treated with surgical removal in certain people, depending on their other risk factors for breast cancer. Risk reduction treatment with endocrine therapy may be offered.