Breast cancer. Image 1 of 2. Coloured mammogram (breast X-ray) showing cancer (red) in the breast. Wires have been inserted into the breast to act as a guide to surgeons during surgery to remove the cancerous tissue. Breast cancer is the most common cancer in women. Symptoms include painless lumps in the breast, and a dark discharge or bleeding from the nipple. Routine screening using mammography can lead to early detection. X-rays are also used during treatment of breast cancer to ensure that the entire tumour is removed. See M122/360 for an image of the excised breast tissue.