Types and differences of Breast Cancer

There are several different types of breast cancer. Some cancer diagnoses are followed by the words in situ, meaning the cancer is contained to a single area, such as a milk duct or lobule, and shows no sign of invasion. If the cancer breaks through the basement membrane that lines the cells from the surrounding lobules or ducts, it is called infiltrating or invasive carcinoma. From there, the cancer can spread to blood vessels, lymph nodes and other parts of the breast. If not detected early, it also can spread to other parts of the body.

The most common types of breast cancer include:

• Infiltrating (or invasive) ductal carcinoma. This form of breast cancer is by far the most common, accounting for 70 to 80 percent of all cases, according to the National Cancer Institute (NCI). As the mass grows, it can lead to a dimpling of the breast or the nipple retracting inward.

• Ductal carcinoma in situ (DCIS). Also known as intraductal carcinoma or non-invasive ductal carcinoma, DCIS refers to cancer cells confined to the milk duct of the breast with no evidence of invasion into the surrounding tissues. DCIS is now a common diagnosis due to the widespread use of screening mammography and usually shows up as calcifications on the mammogram. In situ cancers are noninvasive and are considered the earliest stage of breast cancer.

• Infiltrating (or invasive) lobular carcinoma. This invasive type of breast cancer can be difficult to detect because it often appears as a thickening within the breast and not a clearly defined mass. A small number of women diagnosed with infiltrating lobular carcinoma will develop the disease in both breasts. Lobular carcinoma accounts for less than 10 percent of invasive breast cancers, according the American Cancer Society (ACS).

• Inflammatory breast cancer. This form of the disease is considered a highly malignant type of breast cancer. Inflammatory breast cancer can spread rapidly producing symptoms of swelling and redness and skin that is warm to the touch. The ACS estimates that approximately 1 to 3 percent of all breast cancer diagnoses are inflammatory breast cancer.

• Lobular carcinoma in situ (LCIS). Also known as noninvasive lobular carcinoma, LCIS is more common among premenopausal women and often develops in both breasts or in several areas of one breast. Very few women diagnosed with LCIS develop an invasive form of breast cancer.
In addition to the more common forms of breast cancer, there are other rarer types of invasive breast cancers. These are:

• Paget’s disease. This disease is slow-growing cancer of the areola (pink area around the nipple) and nipple. Starting in the milk ducts of the nipple, Paget’s disease eventually grows onto the nipple itself. It is sometimes mistaken for eczema as it can create itchiness or a crusty appearance around the nipple. This form of breast cancer accounts for about 1 percent of all cases of breast cancer, according to the ACS.

• Medullary carcinoma. This type of infiltrating cancer is characterized by large cancer cells and a distinct margin between cancerous and normal tissue. It accounts for less than 5 percent of breast cancers, according to the ACS.

• Tubular carcinoma. This invasive cancer is a slow-growing form of breast cancer that is tube-shaped. It accounts for approximately 2 percent of all breast cancers, according to the ACS.

• Mucinous (colloid) cancers. This type of breast cancer contains a mucous protein within the cancer cells.

Other, extremely rare breast cancers include:

• Angiosarcoma, which is sometimes referred to as hemangiosarcoma

• Phyllodes tumor, which is normally seen in women of middle age who have a prior medical history of fibroadenomas

• Primary lymphoma

The NCI labels these as tumor subtypes that occur in the breast, but are not considered typical breast cancers.

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Breast cancer

Breast cancer is a growth of abnormal cells, usually within the ducts (which carry the milk to the nipple) or lobules (glands for milk production) of the breast. In more advanced stages of the disease, these out-of-control cells invade nearby tissues or travel throughout the body to other tissues or organs. More than 178,000 women and 2,000 men are diagnosed each year with breast cancer, according to the American Cancer Society (ACS). For women, this rate is second only to non-melanoma skin cancer.

In women, breasts are glands that are capable of producing milk. Each breast is made up of 15 to 20 sections known as lobes. Each lobe contains a number of smaller lobules which contain the milk secreting cells. The milk is then transported to the nipple by ducts. The lobular cells and the ductal cells can both be affected by cancer.

The breasts also contain lymph vessels that transport a clear fluid called lymph through the body to the lymph nodes. Lymph nodes near the breast are found under the arm, above the collarbone and behind the breastbone.

The body’s organs and glands (including breasts) are made up of tissues, which are made up of cells. Normal cell function requires these building blocks to divide and also to die when they grow old – allowing for new cells to take their place in an organized manner. When old cells do not die and the body continues to create new cells it does not need, a mass of cells form a growth or tumor. These tumors do not always signal cancer, particularly in the breast. They can be benign (noncancerous) or malignant (cancerous).
Benign breast lumps are common and may be due to fibrocystic changes in the breast tissue. Most benign breast lumps are fibroadenomas or papillomas. In addition, benign tumors:

• Are rarely life-threatening
• Can be removed and seldom grow back
• Do not spread to tissue around them or to other parts of the body
Malignant tumors have significant differences from benign tumors. Malignant tumors:
• Are generally more serious than benign tumors
• May be life-threatening
• Can often be removed but they can grow back
• Can invade nearby tissues and organs (local invasion)
• Can break away in the form of cells that enter the bloodstream or lymphatic system and travel to other areas (distant metastasis)

Breast cancer begins with a growth of abnormal cells within the breast tissues. The type of breast cancer is determined by where the cancer began – in the ducts, the lobules or other areas, such as the connective tissue or in the blood vessels. It is also important to determine if the cancer has spread beyond the ducts or lobules and invaded nearby lymph nodes.

The lymph nodes are bean-shaped groupings of immune system cells that help the body fight off infections and other threats. A woman’s breast contains both blood vessels and lymph vessels. Within the lymph vessels is a clear fluid called lymph. Fluid from the breast tissue drains through the lymph vessels to the lymph nodes under the armpit, near the breastbone and above the collar bone.

Thus, when breast cancer starts to spread, the most common first location is the nearby lymph nodes. If breast cancer has spread to the axillary lymph nodes (located in the underarm region of the body), it can cause swelling of these nodes. After the cancer cells have spread to the lymph nodes it is more likely that the cancer will spread to other areas as well, such as the lungs, bones or brain.

According to the National Cancer Institute (NCI), breast cancer is the most common cancer among women, excluding non-melanoma skin cancers. It accounts for nearly 1 in 3 cancers diagnosed in women in the United States. Since 1990, the death rate from breast cancer in women has declined. The decreased number of deaths has been attributed to both earlier detection and advances in treatment of the disease.

A study released in 2006 indicated that the incidence, or new cases, of invasive breast cancer declined in the period from mid-2002 to 2003. The ACS statistics for 2001 to 2003 indicate that new breast cancer cases leveled off after 20 years of increases. Many factors may contribute to this change, including changes in early detection or a major decrease in the use of hormone replacement therapy by women after menopause. However, the cause and effect of such changes are difficult to establish, especially in the short term.

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Lung Cancer Kills Non-Smokers Too

Cigarette smoking causes almost 90 percent of all lung cancers. So, it's not surprising that two of my close friends with lung cancer protested, "But I never smoked!"

In the U.S., however, about nine percent of the lung cancers in men and 19 percent in women occur in people who have never smoked -- defined as less than 100 cigarettes over a lifetime.

Other causes of lung cancer

The two most common causes of lung cancer in never-smokers are exposure to second hand smoke and exposure to radon. While second hand smoke is usually avoidable, radon is a natural radioactive gas that you can't see, smell or taste. Radon can seep into houses (usually in the basement) from naturally occurring uranium in the soil. (See: Radon and Lung Cancer.)

Lung cancer in never-smokers differs in at least two major respects from lung cancer in smokers:

* When examined under a microscope, certain types of cancer cells are more commonly found in cancerous tissues of never-smokers than in lung cancers present in smokers.
* Never-smokers more often have mutations in the gene for epidermal growth factor receptor (EGFR). These mutations foster the harmful, uncontrolled growth of cells that is characteristic of cancer.

These differences in microscopic appearance often make it possible to treat lung cancer in never-smokers with drugs that overcome the ill effects of the mutations in EGFR.

Diagnosis often comes late

Lung cancer in both smokers and never-smokers is usually first detected in advanced stages of the disease because the most common symptoms -- cough, chest pain, and shortness of breath -- are not particularly specific. Diagnosis can be delayed even further in never-smokers because doctors may not consider the possibility that they might have lung cancer.

Unfortunately, survival rates appear equally dismal in smokers and in never-smokers. However, some never-smokers do appear to have one therapeutic advantage. Those with mutations in EGFR (as described above) may respond to two drugs, gefitinib (Iressa) and erlotinib (Tarceva). While erlotinib appears more effective, both may be used after unsuccessful chemotherapy, or as primary therapy instead of chemotherapy in some cases.

Preventing lung cancer

Of course, the best way to prevent lung cancer is not to smoke. Also, never-smokers may reduce their chances of lung cancer by avoiding smoke-filled rooms. Finally, check your home for radon, which may be seeping in through fixable cracks in basements or walls. Visit the U.S. Environmental Protection Agency website for more information about radon.

By Simeon Margolis, M.D., Ph.D.

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