What Is Breast Cancer?

What Is Breast Cancer?
Invasive Cancer
Carcinoma In Situ
Lobular Carcinoma In Situ (LCIS)
Ductal Carcinoma In Situ (DCIS)
Mammographic Findings of Breast Cancer
Other Breast Diseases

What Is Breast Cancer?

Breast cancer is a type of cancer where cells in the breast tissue divide and grow without control. About 80 percent of cases of breast cancer originate in the mammary ducts, while about 20 percent arise in the lobules (IOM, 1997). Cancerous tumors in the breast usually grow very slowly so that by the time one is large enough to be felt as a lump, it may have been growing for as much as ten years. One of the most important distinctions to understand is between invasive breast cancer and carcinoma in situ (kar-sin-O-ma in SY-too). In Chapters 5 and 6, the diagnosis of breast cancer and the stages of the disease are discussed in more detail, but below is a brief overview of the key concepts.

Invasive Cancer

When abnormal cells from inside the lobules or ducts break out into the surrounding tissue, the condition is called invasive breast cancer. This term, though, does not necessarily mean that metastases have been found anywhere beyond the breast. When invasive cancer is generally at its most treatable, such as when a tumor is relatively small and has not spread to the lymph nodes, it is considered "early stage." When the condition is more serious and successful treatment less likely, such as when a tumor is very large or has spread to other organs (like the liver, lungs, and bones), it is considered "advanced stage" (IOM, 1997).

In the past, it was thought that breast cancer would usually grow in an orderly progression from a tiny tumor in the breast tissue to a larger one, sequentially traveling out to the nearby lymph nodes, then distant ones, and finally metastasizing in other parts of the body. Now, however, it is thought that cancer cells are capable of traveling from the breast through the blood and lymphatic system very early in the course of the disease; though, these traveling cancer cells do not always survive beyond the tumor (Spratt and Tobin, 1995). For more information on invasive cancer, see Chapter 5: Diagnosis of Breast Cancer and Chapter 7: Treating Breast Cancer.

Carcinoma In Situ

When abnormal cells grow inside the lobules or milk ducts but there is no sign that the cells have spread out to the surrounding tissue or beyond, the condition is called carcinoma in situ. The term "in situ," which means "in place," is used because with carcinoma in situ, the abnormal cells remain "in place" inside the lobules or ducts where they first developed. There are two main categories of carcinoma in situ: ductal carcinoma in situ and lobular carcinoma in situ.

Although the word carcinoma is used in their titles, the cells involved in the different carcinomas in situ are not fully cancerous. They are often referred to as precancerous conditions because they can either develop into or raise the risk of invasive cancer.

Ductal Carcinoma In Situ (DCIS)

Normally the mammary ducts are hollow so that fluid can pass through them. With DCIS, excess cells that are very similar to invasive cancer cells grow inside the ducts. DCIS is not invasive cancer, but it is associated with an increased risk of breast cancer and is considered a precancerous condition that has the potential to develop into invasive cancer eventually. For more information on DCIS, see Chapter 5: Diagnosis of Breast Cancer and Chapter 7: Treating Breast Cancer.

Lobular Carcinoma In Situ (LCIS)

Like the milk ducts, the lobules of the breast tissue have open space inside them. When large numbers of abnormal cells grow in the lobules, the condition is called LCIS. LCIS is not invasive cancer, and it is not a direct cancer precursor, that is, the abnormal cells found inside the lobules are not likely to turn into cancer later on. LCIS is, however, a risk factor for invasive cancer. And, as with other risk factors for the disease (see Chapter 3 for more information on these), women who have LCIS are more likely to develop invasive cancer in either breast.

Increasingly, providers refer to LCIS as "lobular neoplasia in situ," believing this title to be a more accurate depiction of the condition. For more information on LCIS, see Chapter 5: Diagnosis of Breast Cancer and Chapter 7: Treating Breast Cancer.

Mammographic Findings of Breast Cancer

• High density, spiculated mass  (image:  mammogram)
• Clustered microcalcifications with variable shape and size; Granular, bizarre microcalcifications are suspicious.
• Well-defined solid masses are sometimes malignant. (Ultrasound is used to determine whether such a mass is solid or cystic.)

Mammography (image: mammogram) allows the early detection of small, non-palpable breast cancers, and thus, allows identification of breast cancers at an earlier state than physical exam

Women can therefore, have more choices in therapy, including breast conservation therapy (lumpectomy and radiation therapy) and have improved outcomes when compared to breast cancers discovered by physical exam

Comedo-type Intraductal Carcinoma I (image only) 
Intraductal Carcinoma (mammogram) (courtesy Yale School of Medicine)

Other Breast Diseases

There are many breast diseases other than invasive cancer, from infections to excessive cell growth (neoplasms). Some cause discomfort or pain and a woman will seek treatment, while others are of little concern and need no medical attention. Unfortunately, many breast diseases mimic the symptoms of cancer and so require tests and sometimes surgical biopsy to diagnose (see Figures 4.3, 4.4, and 4.5, in Chapter 4 for more information on the steps used to diagnose breast abnormalities). The majority of biopsies result in the diagnosis of a benign (noncancerous) breast disease rather than cancer (see Chapter 5: Diagnosis of Breast Cancer, for more information on biopsies). There are a few that are not dangerous in themselves but do increase the risk for later development of breast cancer. Some of the more common benign breast diseases are hyperplasia, cysts, fibroadenomas, and calcifications (Donegan, 1995).

The term "fibrocystic changes" is used by some health care providers to describe a broad range of different benign breast diseases. Hyperplasia and cysts are often included in this category. Many providers, though, prefer not to use the term at all, since it can encompass such a wide range of lesions that have different effects on cancer risk. If a woman is told she has fibrocystic changes, she should ask for more details about the specific type of fibrocystic change that was identified (for example, whether it is a cyst or hyperplasia) and how it may affect her breast cancer risk.

Hyperplasia

Hyperplasia is the term describing the excessive accumulation (or proliferation) of cells. It is usually found on the inside of the lobules or the ducts in the breast tissue. When the extra cells appear normal (hyperplasia), the condition is not precancer. Sometimes the excess cells in the lobules or ducts are abnormal, and this condition is called atypical hyperplasia. Atypical hyperplasia is a condition in the middle ground between too many normal cells (hyperplasia) and too many abnormal cells (carcinoma in situ). Atypical hyperplasia cells bear some resemblance to DCIS, though they still have enough normal features that they do not meet the criteria for carcinoma in situ (Donegan, 1995). Hyperplasia that is not atypical is associated with approximately double the risk for breast cancer, while atypical hyperplasia is associated with 3.5-5 times the risk (Colditz, 1993; Marshall et al., 1997; Page el al, 1985). See Chapter 4: Early Detection, for more information on detecting and diagnosing hyperplasia.

Cysts

Cysts are sacs filled with fluid that are almost always benign. Often they can be left alone, or if painful, they can be drained of the fluid (aspirated). Up to a third of women between the ages of 35 and 50 have cysts in their breasts, though most are too small to feel and can be detected only by ultrasound examination. (For more on ultrasound, see Chapter 4.) If cysts are large enough, they may feel like lumps in the breast. In a small proportion of women, the cysts will recur after being aspirated. If this happens repeatedly, a woman may want to have them removed. Cysts are more common in women as they approach menopause, but they are not associated with an increased risk of cancer. After menopause, cysts occur much less frequently (Donegan, 1995).

It is unknown exactly what causes cysts to develop. Although certain dietary factors, such as caffeine intake, have been discussed as possible risk factors for developing breast cysts, there is currently very little data backing up any link between cyst development and either dietary or lifestyle factors (Ernster et al., 1982; Heyden et al., 1986; Hislop et al., 1990). See Chapter 4: Early Detection, for more information on detecting and diagnosing cysts.

Fibroadenomas

Fibroadenomas, another type of benign lump, are most common in younger women. They are usually not removed because they pose no risk. Sometimes they are uncomfortable and produce a lump that can be felt in the breast. If a fibroadenoma is large, a woman will probably want it removed. In older women, fibroadenomas are generally removed to be certain they are not malignant tumors. Fibroadenomas are not generally associated with an increased risk of cancer (Donegan and Spratt, 1995). See Chapter 4: Early Detection, for more information on detecting and diagnosing fibroadenomas.

Calcifications

Most calcifications are just randomly scattered bits of calcium in the breast. In older women especially, calcium may leave the bones and appear in other parts of the body, such as joints or breasts. But clusters of tiny calcifications (microcalcifications) can be indications of precancer or cancer. Microcalcifications usually form as small, tight clusters in the ducts that can be seen on a mammogram. Although they are not themselves dangerous, they can be a warning sign of cancer and lead a doctor to perform follow-up tests to determine whether the area is cancerous or not (Donegan, 1995). See Chapter 4: Early Detection, for more information on detecting and following up calcifications.

Diagnosis of a Benign Breast Condition When cancer is suspected, the diagnosis of a benign breast condition can bring psychological and emotional relief. Benign breast conditions can include many different types of lesions, including fluid-filled cysts, hyperplasias, and fibroadenomas. Although the diagnosis of a benign breast condition can be somewhat disconcerting in its own right, the majority of these conditions do not directly increase risk for breast cancer. Of the benign conditions that do increase risk, the lesion that imparts the highest risk (atypical hyperplasia) accounts for only a small percentage of benign breast conditions diagnosed.