Tumor Staging - Making The Diagnosis: Breast Cancer

Content provided by the Faculty of the Harvard Medical School

Tumor staging

Staging is a standardized method used to:

• Describe the level of advancement of a cancer

• Define characteristics of the cancer itself (e.g. size)

• Determine whether the cancer has spread beyond the confines of the tissue in which it arose.

Staging helps doctors determine your prognosis and how to treat the cancer. If the cancer is invasive, your doctor may request other tests, such as a chest x-ray and blood tests, to help determine whether the cancer has metastasized, or spread to the lungs, bones, or liver. Bone scans and CT scans are reserved for more advanced tumors, when abnormalities are seen in the blood tests or x-rays, or when the patient is having symptoms that suggest the cancer may have spread. Information from such tests, along with examination of the cancerous tissue, is used to help determine the stage of the cancer.

The pathologist examines the tissues and assigns a series of letter and number codes that provide a standardized, shorthand way of describing it. The letters and numbers describe the size of the tumor, whether the lymph nodes are involved, and the possibility of metastases elsewhere in the body.

The staging system has been revised to determine many different characteristics, such as the number of lymph nodes that contain cancer, the size of the lymph node, as well as the extent of the individual lymph node with cancer cells. Small clusters of cells, called micrometastases, are considered less serious than larger tumors in the regional lymph nodes, called macrometastases. Both are different from distant metastases, which are cancers that have spread away from the breast to other organs, such as the bones, liver, lungs, or brain.

Doctors use the following letter designations (The TNM System):

• T, for invasive Tumor size

• N, for extent of lymph Node involvement (includes micrometastases and macrometastases)

• M, for presence or absence of distant Metastases (bone, lung, liver, brain).

The use of the TNM system uses two models: the pathological model and the clinical model. When a pathologist receives a specimen, for example, from the breast, a determination can be made that describes:

• The size of the tumor(s)

• Differentiation. Well differentiated cancer cells have an appearance closer to normal tissue and tend to behave in a less aggressive manner. Poorly differentiated cancer cells have little resemblance to the tissue they arose from and usually indicate aggressive growth and less favorable prognosis.

• The number of lymph nodes that may accompany the specimen and the number and size of lymph nodes involved with cancer.

Based on these factors, the pathologist assigns a pathological assessment of the tumor and node status, so called pTN. If there is no tissue of distant organ sites, such as the liver or lung, the determination of the presence of metastases cannot be determined, providing the designation MX (meaning that a determination of the presence or absence of metastases cannot be made.)

The clinical or cTNM takes into consideration the TN as determined by the pathologist. It also includes the "staging" studies that the oncologist may have ordered and evaluated - the "M" in TNM. Here is an example: Following breast surgery a woman shows spread of cancer to the liver on CT scan of the abdomen. This gives her stage M1 diseases, in addition to the T and N determinations from the pathologist.

These designations are then combined to determine a stage (Stage I, Stage, II, and so on) according to the extent of the cancer. Stages are given in Roman numerals, the higher the number, the more advanced the cancer. The staging system gives a picture of the patient's disease and the probable long-term outcome. However, staging cannot determine when the cancer metastasized, when it was diagnosed, or what the response to treatment will be.

Because of the complexity of this system, doctors in the past have sometimes described the cancer in simpler terms, referring to the size of the tumor and the number of positive nodes (nodes that show cancer). For example, a woman may be said to have a 2-centimeter tumor with three positive nodes. Recognize that this is an over simplification. Today, it is considered incomplete. It does not provide adequate information when doctors from different specialties discuss the best treatment approaches.

Last updated:	April 23, 2007