Breast cancer: mammogram of a female breast showing the localization of a needle in a non- invasive cancerous tumour. Mammography is a special X-ray technique that is used to visualize soft tissues of the breast as a means of screening for breast cancer. It is also used to obtain a needle aspirate of cells for subsequent examination under the microscope. The majority of breast cancers originate in the mammary ducts; the breast lobular glands are also affected. Most tumours of either type show early evidence of invasive (malignant) behaviour, but ductal & lobular cancers may exist in non-invasive forms.