Breast cancer. Coloured magnetic resonance imaging (MRI) scan of the breast of a 50 year old woman with breast cancer. The malignant (cancerous) tumour (yellow, lower centre) has been highlighted by the contrast medium gadolinium. Breast cancer is the most common type of cancer in women. The cancer can invade surrounding tissue and spread to other parts of the body (metastasis). Treatment is with removal of the tumour only, where possible, or complete removal of the breast. Surgery is often combined with radiation therapy and chemotherapy.