An aggressive cancer of the breast ducts, called invasive ductal carcinoma, is the most common form of breast cancer, accounting for four out of five breast cancer diagnoses, according to Johns Hopkins Medicine. The cancer usually develops as a tumor within a single breast duct, but can then spread to multiple ducts, forming a large breast tumor. Left undetected, the cancer can eventually spread to lymph nodes around the breast and eventually travel to distant tissues.
DCIS
Invasive ductal carcinoma can develop due to an existing breast tumor, such as ductal carcinoma in situ, or DCIS. DCIS tumors contain cancerous cells that have not yet begun to invade into other tissues within or outside the breast, according to BreastCancer.org. Left untreated, a DCIS tumor may continue to grow and eventually begin to migrated into other tissues, becoming an invasive ductal carcinoma. Women can help prevent the development of DCIS into a more invasive tumor by performing monthly breast self-examinations to check for breast lumps or abnormal nipple discharge, and undergoing regular clinical examinations and mammograms to detect any tumor growth early in its development.
Inherited BRCA1/2 Mutations
Another possible cause of invasive ductal carcinoma is an inherited genetic mutation, such as mutation to BRCA1 or BRCA2. These genes normally act as tumor suppressors--when a breast cell develops a genetic mutation, BRCA1 and 2 allow the cell to repair this mistake before further cell division, and prevent the cell from accumulating genetic mutations and forming an invasive ductal carcinoma. Patients who inherit a mutation to either BRCA1 or to BRCA2 have a greatly increased risk of developing breast cancer, as well as increased risk of developing pancreatic, cervical, uterine or colon cancers. Individuals with an extensive family history of these cancers may consider genetic testing for BRCA1 or BRCA2 mutations, to asses their susceptibility for invasive ductal carcinomas and other breast cancers.
ErbB2 Mutations and Overproduction
Mutations to other genes, such as ErbB2, may also cause invasive ductal carcinoma. The ErbB2 gene codes for a protein called HER2, which sits at the surface of the breast cell and, when active, promotes cell proliferation. Many women with breast cancer develop mutations to HER2 that cause an over-production of the protein. With greatly enhanced amounts of HER2 in these mutant breast cells, the cell constantly receives signals to promote cell proliferation and can eventually develop into an invasive ductal carcinoma. The breast cancer drug Herceptin is designed to target and kill breast cancers that over-produce the HER2 protein, effectively treating invasive breast cancers.
