Friday, October 9, 2009

Types of Breast Cancer

Your doctor suspects that you have breast cancer. To confirm the diagnosis, a pathologist analyzes a tissue sample (biopsy) taken from the lump or suspicious area in your breast. This will tell if you have cancer or some other, benign condition. If the biopsy does show cancer, the results provide your doctor with information about the type of breast cancer and help determine treatment options.

The biopsy results appear on a pathology report, which provides detailed information including the type of breast cancer, if it's invasive or noninvasive, the tumor grade - how closely the cancer cells resemble normal tissue - if the cancer is sensitive to hormonal therapies and if it has too much of a protein called HER‑2. Sophisticated lab tests can also analyze breast cancer tissue for molecular and genetic features of breast cancer cells. Understanding all these aspects of a cancer helps your doctor tailor your treatment plan.

Common types of breast cancer

The most common types of breast cancer begin either in your breast's milk ducts (ductal carcinoma) or in the milk‑producing glands (lobular carcinoma). The point of origin is determined by the appearance of the cancer cells under a microscope.

In situ breast cancer

In situ (noninvasive) breast cancer refers to cancer in which the cells have remained within their place of origin - they haven't spread to breast tissue around the duct or lobule. The most common type of noninvasive breast cancer is ductal carcinoma in situ (DCIS), which is confined to the lining of the milk ducts. The abnormal cells haven't spread through the duct walls into surrounding breast tissue. With appropriate treatment, DCIS has an excellent prognosis.

Invasive breast cancer

Invasive (infiltrating) breast cancers spread outside the membrane that lines a duct or lobule, invading the surrounding tissues. The cancer cells can then travel to other parts of your body, such as the lymph nodes.

Invasive ductal carcinoma (IDC). IDC accounts for about 70 percent of all breast cancers. The cancer cells form in the lining of your milk duct, then break through the ductal wall and invade nearby breast tissue. The cancer cells may remain localized - staying near the site of origin - or spread (metastasize) throughout your body, carried by your bloodstream or lymphatic system.

Invasive lobular carcinoma (ILC). Although less common than IDC, this type of breast cancer invades in a similar way, starting in the milk‑producing lobules and then breaking into the surrounding breast tissue. ILC can also spread to more distant parts of your body. With this type of cancer, you typically won't feel a distinct, firm lump but rather a fullness or area of thickening.

Not all types of breast cancer begin in a duct or lobule. Less common types of breast cancer may arise from the breast's supporting tissue, including the fibrous connective tissue, blood vessels and lymphatic system. In addition, some tumors don't actually begin in the breast but represent a different type of cancer that has spread (metastasized) from another part of the body, such as the lymphatic system (non-Hodgkin's lymphoma), skin (melanoma), colon or lungs. These are not called breast cancer but are referred to as cancer from where it started, now metastatic to the breast.

Unusual types of breast cancer include inflammatory breast cancer, phyllodes tumor, angiosarcoma, osteosarcoma, metaplastic breast cancer, adenoid cystic carcinoma and Paget's disease of the breast. There are also rare subtypes of invasive ductal carcinoma — tubular, mucinous, medullary and papillary.

If the cancer is an invasive type, the pathologist assigns it a grade. The grade is based on how closely cells in the sample tissue resemble normal breast tissue under the microscope. The grading information, along with the cell type, helps your doctor determine treatment options.
Breast cancers are graded on a 1 to 3 scale:
Grade 1. The cells still look fairly normal (well differentiated).
Grade 2. The cells are somewhat abnormal (moderately differentiated).
Grade 3. The cells have lost their proper structure and function (poorly differentiated).
The pathologist determines the grade by looking at the size and shape of both the cell and its nucleus and counting how many cells are in the process of dividing. A higher grade suggests a faster growing cancer that's more likely to spread. Breast cancers are tested for the presence of estrogen and progesterone receptors. A receptor is a protein on the outside of a cell that can attach to specific chemicals, hormones or drugs traveling through the bloodstream.

Normal breast cells and some breast cancer cells have receptors that bind to the female hormones estrogen and progesterone. The hormones signal the cells to increase or "turn on" cell growth. Breast cancers can be hormone receptor (HR) positive or HR negative. Tumors found to be HR positive are further categorized as estrogen receptor positive (ER positive) or progesterone receptor positive (PR positive). With ER positive or PR positive breast cancer, hormone-blocking medications, such as tamoxifen, slow the cancer's growth. Hormone receptor positive cancers typically grow more slowly than do HR negative cancers.

Knowing if a cancer has too many copies of the HER-2 gene also influences treatment decisions. This gene drives production of the growth-promoting HER-2 protein. About one out of every five breast cancers is HER-2 positive, meaning these cancers have greater than normal amounts of the HER-2 protein. These cancers tend to grow and spread more aggressively than do other cancers.

The goal of much current breast cancer research is to understand the characteristics of cells in individual tumors. By applying the latest in molecular technology, researchers can identify genes associated with breast cancer and measure their activity in tissue samples. Tools called microarray analysis and reverse transcriptase-polymerase chain reaction (RT-PCR) are used to study patterns of behavior, or expression, of large numbers of genes in breast tissue samples. The researchers can then identify a set of genes whose activity provides information about a cancer, such as the likelihood of recurrence. These tests, known as genetic profiling or gene-expression profiling, have so far been used only for a minority of breast cancers.

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