What is Breast Cancer?

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Tumors • Growth Rate • Types of Breast Cancer • How Cancer Spreads

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Tumors
All organs in the body are made of cells. Individual cells are so small, they can be seen only through a microscope. Normally, cells divide in an orderly fashion to replace cells that have aged and died. Controls within each cell tell it to stop dividing if no new cells are needed.

Occasionally, damage to DNA during cell duplication may cause the controls to malfunction. Cells begin to divide uncontrollably, forming lumps or tumors.

The word "tumor" comes from a Latin word that means "swelling." A tumor could be composed of cells that divide excessively, but that do not invade or damage other parts of the body. A good example is a fibroid in the uterus, or a fibroadenoma in the breast. Both of these are called benign, that is, non-cancerous tumors.

Malignant tumors are composed of aggressively dividing cells that destroy surrounding tissues or travel to other parts of the body. In general conversation, the word "tumor" is often used to refer to a malignant condition, or cancer.

 

 

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Growth Rate
Growth rate is the speed at which a lump or tumor grows. Different types of breast cancer grow at different rates. The time it takes for a tumor to become twice as large is called doubling time. The average doubling time for most breast cancer tumors is in the range of 50 to 200 days.

The change of the first normal cell into a malignant cell happens years before any evidence of cancer can be detected by any tests that we have today. It may take three to five years for a cluster of cancerous cells to become large enough to be seen on a mammogram. In other words, by the time your cancer has been detected, it has been there for several years. That is why there is no harm in taking a few more weeks to decide on the best treatment possible.

 

 

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Types of Breast Cancer
Breast cancer types are named according to the part of the breast in which they develop. The most common forms of breast cancer come from cells that line the milk ducts (ductal cancer) or the milk-producing lobules (lobular cancer).

In the early stages, cancer cells divide locally, and do not cross the wall of the duct or lobule. This type of cancer is called in situ (meaning "in place"). Once the cancer cells cross the lining of the duct or lobule, they are called infiltrating, or invasive. Do not be unduly alarmed if you are told your cancer is "invasive." Most cancers are, so your invasive cancer is the "normal" cancer. Today about one in five cases of diagnosed breast cancers fall into the non-invasive, or in situ category—either ductal carcinoma in situ (DCIS), or lobular carcinoma in situ (LCIS).

DCIS cancers are highly curable. Some physicians don't even refer to them as cancer, but rather as "precancerous lesions," since DCIS may never progress to be an invasive cancer. The treatment of DCIS may not follow the same plan as for invasive cancers, so we have dedicated a separate chapter to this non-invasive form of the disease. You still need to read the chapters on staging, surgery and radiation to understand the principles involved.

LCIS is a non-invasive growth that is not considered cancerous, but women who are diagnosed with LCIS have about a 1% per year risk of developing invasive breast cancer. That means that twenty years after diagnosis, the risk is about 18%. What is important to know is that the invasive cancer can occur in either breast, and not necessarily where the LCIS was originally found. In other words, LCIS is not a precursor, but a marker. Infiltrating or invasive cancers, where malignant cells cross the lining of the duct or lobule, are more advanced than in situ cancers. They invade, or infiltrate, adjacent tissues. The most common type of breast cancer is the infiltrating ductal carcinoma. More than half of all cases are of this type.

Other types of breast cancer are less common. One example is Paget's Disease, a cancerous growth that first appears as scaling on the nipple, and may be confused for a simple rash. Another is inflammatory cancer, a rare form of cancer that grows quickly, causing redness and swelling of the breast. This is really the only form of breast cancer in which the treatment decision needs to be made as soon as possible.

 

 

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How Cancer Spreads
As a malignant tumor grows, it may spread locally, invading and sometimes destroying other tissues, or cells may break away from the tumor and get into the lymphatic vessels, or into the blood vessels, and travel to distant parts of the body. Some of the breakaway cells will be trapped in the lymph nodes of the armpit, or axilla. Examination of these nodes by a procedure called axillary lymph node dissection, can help determine the stage (the degree of spread) of the cancer.

If cancer cells escape beyond the lymph nodes, or enter the circulatory system directly, they can spread to the liver, brain, lungs, and bones, forming new tumors called metastases. These distant metastases are the most worrisome, because they can damage vital organs. This advanced stage of breast cancer, called metastatic cancer, is less common and its management is more difficult.

To make sure that no cancer cells remain anywhere in the body, it is often necessary to use systemic therapy—therapy that reaches all the organs, in all parts of the body, by means of the blood stream. This is explained in the Chemotherapy and Hormone Therapy sections.

 

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