Long-term estrogen therapy, a high fat diet, and alcohol use have been reported as possible risk factors, but the extent of their relationship to the onset of breast cancer remains unclear. The diagnosis of breast cancer can only be made by pathological examination of breast tissue. A lump in the breast usually warrants biopsy even when the mammogram is described as being normal. Breast tissue may be obtained by needle aspiration biopsy or surgical biopsy. Needle aspiration is used by some physicians to help differentiate between cysts and solid tumors.
Cysts frequently disappear after aspiration and the removal of fluid.
Cytological or pathological examinations of material removed in the aspiration can be used to identify the cancer. Ultrasound may help determine whether the lump is solid or cystic. Surgical biopsy is generally performed under general or local anesthesia in an ambulatory surgical center. Excisional biopsy , the most commonly performed procedure, is used when lumps are small. In these cases, the entire tumor and a margin of normal tissue is excised.