How is breast cancer diagnosed and staged

Once a patient has symptoms suggestive of a breast cancer or an abnormal screening mammogram, she will usually be referred for a diagnostic mammogram. A diagnostic mammogram is another set of x-rays with additional angles and close-up views. Often, and ultrasound will be performed during the same session. An ultrasound uses high-frequency sound waves to outline the suspicious areas of the breast. It is painless and can often distinguish between benign and malignant lesions.
Depending on the results of the mammograms and/or ultrasounds, your doctors may recommend that you get a biopsy. A biopsy is the only way to know for sure if you have cancer, because it allows your doctors to get cells that can be examined under a microscope. There are different types of biopsies; they differ on how much tissue is removed. Some biopsies use a very fine needle, while others use thicker needles or even require a small surgical procedure to remove more tissue. Your team of doctors will decide which type of biopsy you need depending on your particular breast mass.
Once the tissue is removed, a doctor known as a pathologist will review the specimen. The pathologist can tell if is the cells are cancerous or not, If the tumor does represent cancer, the pathologist will characterize it by what type of tissue it arose from, how abnormal it looks (known as the grade), whether or not it is invading surrounding tissues, and whether or not the entire lump was removed during surgery. The pathologist will also test the cancer cells for the presence of estrogen and progesterone receptors as well as a receptor known as HER-2/neu. The presence of estrogen and progesterone receptors is important because cancers that have those receptors can be treated with hormonal therapies. HER-2/neu expression may also help predict outcome. There are also some therapies directed specifically at tumors dependent on the presence of HER-2/nue. See Understanding Your Pathology Report for more information.
In order to guide treatment and offer some insight into prognosis, breast cancer is staged into five different groups. This staging is done in a limited fashion before surgery taking into account the size of the tumor on mammogram and any evidence of spread to other organs that is picked up with other imaging modalities; and it is done definitively after a surgical procedure that removes lymph nodes and allows a pathologist to examine them for signs of cancer. The staging system is somewhat complex, but here is a simplified version of it:
Stage 0 (called carcinoma in situ)
Lobular carcinoma in situ (LCIS) refers to abnormal cells lining a gland in the breast. This is a risk factor for the future development of cancer, but this is not felt to represent a cancer itself.
Ductal carcinoma in situ (DCIS) refers to abnormal cells lining a duct. Women with DCIS have an increased risk of getting invasive breast cancer in that breast. Treatment options are similar to patients with Stage I breast cancers.
Stage I : early stage breast cancer where the tumor is less that 2 cm, and hasn't spread beyond the breast
Stage II : early stage breast cancer in which the tumor is either less than 2 cm across and has spread to the lymph nodes under the arm; or the tumor is between 2 and 5 cm (with or without spread to the lymph nodes under the arm); or the tumor is greater than 5 cm and hasn't spread outside the breast
Stage III : locally advanced breast cancer in which the tumor is greater than 5 cm across and has spread to the lymph nodes under the arm; or the cancer is extensive in the underarm lymph nodes; or the cancer has spread to lymph nodes near the breastbone or to other tissues near the breast
Stage IV : metastatic breast cancer in which the cancer has spread outside the breast to other organs in the body
Depending on the stage of your cancer, your doctor may want additional tests to see if you have metastatic disease. If you have a stage III cancer, you will probably get a chest x-ray, CT scan and bone scan to look for metastases. Each patient is an individual and your doctors will decide what is necessary to adequately stage your cancer.