Understanding Breast Cancer
Structure: Ducts and Lobules
The breast is made up of tissue reaching from the collarbone to the lower ribs.
This tissue mainly consists of lobes, ducts and fat. Each breast lobe contains groups of milk glands called lobules. The lobules are connected to thin tubes that carry milk to the nipple. These tubes are called ducts, and the ducts and lobes are known as glandular tissue. Fat cushions the internal structures of the breast, which also contains connective tissue, arteries, veins and nerves.
Another important part of the breast is the lymphatic system. This is a system of channels that carry a clear fluid called lymph throughout the body. The fluid is carried to small bean-shaped structures called lymph nodes. Lymph nodes trap waste from the body and work to remove it. Lymph from the breast drains primarily to the lymph nodes in the underarm referred to as axillary lymph nodes. Lymph from the breast also can drain to lymph nodes in the middle of the chest (internal mammary lymph nodes) and to lymph nodes above the collarbone (supraclavicular lymph nodes).
What is a breast cancer?
The body is made up of many types of cells, including the cells that make up the structures within the breast. Cells normally grow and divide to make new cells in a controlled and orderly manner. Sometimes cells are produced when they are not needed. As a result, a mass of extra tissue called a tumor may develop. A tumor can be benign (not cancer) or malignant (cancer).
Malignant (cancerous) tumors consist of abnormal cells that divide without control or order. These cancer cells can invade and damage nearby tissues and may spread to other parts of the body through the blood or lymphatic systems. Breast cancer can develop within the ducts of the breast or within the lobules. Thus, there are two main types of breast cancer: ductal and lobular. There also are other more rare types of breast cancer as well.
Invasive vs. In Situ
Breast cancers are categorized as invasive or in situ.
In situ (non-invasive) cancer is an early stage of breast cancer that has not spread outside of the duct or lobule. In situ cancer in the duct is referred to as ductal carcinoma in situ or DCIS. In situ cancer in the lobule is referred to as lobular carcinoma in situ or LCIS.
In some cases, ductal carcinoma in situ may become invasive cancer. Most often, lobular carcinoma in situ indicates that a woman may develop cancer anywhere in her breasts.
Invasive breast cancers have broken outside of the duct or the lobe and spread into nearby breast tissue. This type of cancer requires treatment to prevent it from spreading. A diagnosis of invasive cancer does not mean that the cancer has spread outside of the breast. Invasive breast cancer means the cancer has spread outside of the ducts and lobules into nearby breast tissue. More testing is needed to determine whether the cancer has spread beyond the breast to the lymph nodes or other parts of the body.
Lymph Node Status
If there is a chance the cancer has spread beyond the breast, the lymph nodes will be tested. This is done by biopsying or removing the lymph nodes in the underarm area. The most common surgery for this purpose is called a sentinel lymph node mapping and excision of sentinel nodes. This identifies the first lymph node(s) that receive lymph fluid draining from the breast. This sentinel node(s) is the most likely place to find cancer if it is spreading beyond the breast. A lymph node that contains cancer cells is called positive
Receptors: ER, PR, and HER2/neu
Cells in the breast have receptors for the female hormones estrogen (ER) and progesterone (PR). These receptors respond to changing hormones during a woman’s life cycle to allow breast tissue to change and grow. If breast cancer cells have high levels of the estrogen or progesterone receptors, then the cancer cells can grow. The receptor status of the tumor is one factor for determining treatment options.
HER2/neu, which stands for Human Epidermal Growth Factor 2, is another receptor that helps cells grow. Too much HER2/neu (called overexpression) can cause cancer cells to grow faster. If a cancer is positive for HER2/neu, a certain medication may be given to treat the cancer using these receptors.
Cancer cells are graded based on how they look under the microscope. Grade 1 cancer cells are most like normal cells and tend to grow slowly. Grade 2 tumors are intermediate grade or appearance. Grade 3 tumors are most different from normal cells and tend to grow more rapidly. Tumor grade is not the same as tumor stage.
The stage of the cancer describes the size of the cancer and how far it has spread in the body.
Although there are several methods of staging, most doctors use the TNM method. The TNM method is based on the size of the tumor (T), the spread of the cancer into nearby lymph nodes (N), and the spread of the cancer to other body parts (M, for metastasis).