A breast lump may either be a cyst filled with fluid or a solid mass of tissue. A sample of the breast tissue (biopsy) must be made to determine whether malignant (cancerous) cells are present. Almost two-thirds of all breast lumps are benign but the chance of a malignant lump is greatly increased if the woman is past menopause.

While the patient is awake and pain-free (using local anesthesia) or asleep and pain-free (using general anesthesia), an incision is made over the lump.

The incision for a lumpectomy is usually around 3 to 4 centimeters long. The incision will also depend on the size of the lump that needs to be removed. After the lump is removed in one piece, it is sent to the laboratory for immediate examination. If the lump is found to be cancerous nearby lymph nodes will be removed to check for the extent of the cancer spreading.