How does breast cancer develop exactly?

Breast cancer: This question gets into the dna level of tumor formation. Basically, any tumor starts with a cell that somehow loses its aability to stop dividing thereby making copies of itself. So a tumor cell just keeps dividing thereby increasing its numbers exponentially over time. Cont'd....

Breast cancer: Cont'd: cancer cells are unique in that they also develop the ability to break off form the mother cell, land somewhere, and grow into new tumors by just continually dividing like the mother cell. This is called metastasis.

Type of cancer: Breast cancer is a type of cancer which originates in the ductal lining of the breast. Cells become abnormal and then become invasive and spread outside the ducts. Cancer cells can then travel to distant sights in the body through the lymphatic channels.