Читать книгу The SAGE Encyclopedia of Stem Cell Research - Группа авторов - Страница 216

Breast cancers are classified by two major categories depending on where they originate in the breast. Malignant breast tumors are common in postmenopausal women and arise from mammary duct epithelium or lobular glands. They are usually the result of overexpression of estrogen and progesterone receptors or erb-B2 (or HER-2, an epidermal growth factor receptor). Axillary lymph node involvement is the single most important prognostic factor in breast cancer. Risk factors for malignant breast tumors include increased exposure to estrogen.

The majority of patients with breast cancer have cancer that originated in the milk ducts of the breast. This type of cancer is called ductal carcinoma, and there are two subtypes: invasive and noninvasive. The noninvasive type of ductal carcinoma is named ductal carcinoma in-situ (DCIS). This type of cancer arises from ductal hyperplasia, which fills the ductal lumen and is considered noninvasive because it does not spread to other tissues of the breast. The second type of ductal carcinoma is named invasive ductal carcinoma and is characterized by the spread of the cancer through the walls of the milk ducts into other tissues of the breast. This results in a firm, fibrous, hard mass with sharp margins and small, glandular duct cells. Invasive ductal carcinoma is the most invasive and most common, accounting for over 75% of breast cancers.

The second major category of breast cancers comes from cancers that originate in the lobules of the breast. The lobules are the parts of the breast responsible for lactation, or the production of milk. Cancers of this type are called lobular carcinomas. Similar to ductal carcinoma, lobular carcinoma contains also two subtypes of the cancer: lobular carcinoma in-situ and invasive lobular carcinoma. Invasive lobular carcinoma is similar to invasive ductal carcinoma in that it spreads outside the lobules of the breast into other tissues. It differs, though, in that there is not a lump that is associated with the cancer. Instead of creating a lump, the cancer cells cause the tissues of the breast to thicken. There are often multiple lumps, and it is often bilateral. Women diagnosed with invasive lobular carcinoma may experience a firmness or unusual fullness of the breast. Lobular carcinoma in-situ differs from the other types of cancers in that it is not, in fact, a cancer. Although there is a presence of abnormal cells in the lobules of the breast, they are noncancerous. Receiving a diagnosis of lobular carcinoma in-situ is certainly better than other types of breast cancers. Although lobular carcinoma in-situ is noncancerous, it does indicate a considerably higher risk for the patient to develop another type of breast cancer. Although these are the two principal categories of origination for breast cancers, there are rare occurrences in which the cancer originates from areas other than the milk ducts and lobules.

Medullary breast cancer demonstrates lymphatic infiltrate on histology and has good prognosis. Comedocarcinoma is a subtype of DCIS that involves ductal caseous necrosis. Lymphatic dermal invasive by breast carcinoma is known as inflammatory breast cancer. This type of breast cancer is characterized by the skin turning into a texture that resembles an orange peel (and is commonly termed peau d’orange). The survival rate for this type of cancer at five years is approximately 50%. Paget’s disease of the breast presents with eczematous patches on the nipple and is a sign for an underlying carcinoma.