A type of breast cancer that starts in a milk duct of the breast.

Ductal carcinoma is the most common type of breast cancer. It includes ductal carcinoma in situ, which means the cancer cells are confined inside a milk duct. When the cancer cells break out and spread into the breast tissue it becomes invasive ductal carcinoma.

Symptoms include a breast lump, nipple discharge and changes in the size, shape and appearance of the breast. Sometimes there are no symptoms. It might be detected on a mammogram.

Treatments might include surgery, radiation and medicines. Medicines used for breast cancer include chemotherapy, hormone therapy, targeted therapy and immunotherapy.