Breast cancer. Coloured breast X-ray (mammogram) of a large malignant tumour (blue area to right of ribs) in a woman's breast. The patient's ribs are visible on the left. Mammography is a special X- ray technique used to investigate lumps in the breast and to screen women for breast cancer. Breast cancer is the most common cancer in women, affecting 1 woman in 20. Successful treatment depends on detecting the cancer before it has spread. Treatment includes lumpectomy (removing the lump), mastectomy (removing a breast), radiotherapy and anticancer drugs.