Breast cancer is the second most common malignancy affecting women worldwide. The interaction between genes and environmental interaction plays an important role in cancer predisposition. Breast cancer patients are subclassified into two classes:

--> Hereditary breast cancer results from mutations in **G**high penetrant genes such as *L*BRCA1 and BRCA2. This has been well documented by the study of large kindreds with multiple affected individuals in varying ethnic groups. Further, specific mutations have been identified within these groups. For instance, three founder mutations have been identified in the Ashkenazi Jewish population. It has been reported (where?) that female mutation carriers have a life-time breast cancer risk of 60-80% for high penetrance mutations.

--> The non-hereditary forms of breast cancer are the 'sporadic' cases due to mutations in a large number of *G*low penetrant variants. A small number of syndromes also come under this category.

A strong family history, early puberty and late menarche are the major risk factors for breast cancer in women. Clinical examination, mammogram and biopsy are techniques used to diagnose breast cancer. Standard treatment options are (*enumerate these*). Cancer gene therapy is now emerging as a therapeutic approach for correcting defects at the gene level.

Epidemiological studies have documented extensively the incidence of breast cancer in the Western population. **but nothing here***

Understanding Breast cancer

Normal cells in the body divide in our body for various reasons such as replacement of aging tissue and increased metabolic demands. However, when cell division is unchecked, the result is cancer. Cancer may thus be defined as an abnormal proliferation of cells, which results from uncontrolled cell division. The three general mechanisms of cancer are

impairment of DNA repair pathway
transformation of a normal gene into a oncogene
malfunction of a tumour supressor gene.

When any one of these processes occur in the breasts, breast cancer may follow. To understand the disease process in detail, a brief knowledge of the breast morphology is essential.

Breast tissue is broadly divided into two regions:
a. Glandular region
b. Fatty region

The glandular region is anatomically divided into sections called lobes which are further subdivided into smaller sections called lobules. These lobes and lobules connect to the nipple via structures called ducts. Breast cancer is called as lobular carcinoma if the malignant cells arise from the lobules, and ductal carcinoma if it arises from the ducts. Breast cancers are also divided into in situ (benign) and invasive carcinomas. In situ means in place (i.e.) the tumorous cells stay inside the carcinoma and do not spread, whereas invasive carcinoma results in metastasis (spread of the tumor).

Cancer in one breast increases the chances of getting in the other breast. Breast cancer can strike both males and females, although women are about 100 times more likely to develop the disease than men. The burden of breast cancer remains high for women throughout the world

Breast cancer is classified in stages numbered from 0 to IV.

Stage 0 is a non-invasive tumor. In ductal carcinoma in situ (DCIS), cancer cells are located within the duct and do not spread. Similarly lobular carcinoma in situ (LCIS) (also called lobular neoplasia) does not spread beyond the lobules
Stage I is a small locally invasive tumor measuring less than 2 cm without lymph node involvement.
Stage II is a medium-sized tumor with or without nodal metastases,
Stage III cancer is a locally advanced cancer, usually with axillary node metastases.
Stage IV cancer has already metastasized to distant sites

The survival rate is dependent upon the classification (stage) of the breast cancer upon diagnosis.

The American Joint Committee on Cancer (AJCC) has classified cancer in the stages above based on therapeutic considerations, estrogen and progesterone receptor status, lymph node status and the general health of the patients.

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Understanding Breast cancer