Breast cancer. Image 2 of 2. Coloured X-ray of excised breast tissue containing a cancerous tumour (dark region at centre of the tissue). Wires were inserted into the breast to guide surgeons to the cancerous tissue during surgery. 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. X-rays are used in diagnosis and treatment of breast cancer. An X-ray of the excised tissue is performed to check that all of the abnormal tissue has been removed. See M122/359 for an image of the breast with the guide wires in place before surgery.