Bone Cancer Stages

As with other kinds of cancers, to find out what kind of treatment is needed for bone cancer, it is necessary to determine if the cancer has started to spread and measure its expansion. This is called cancer staging. The stages of bone cancer are enumerated according to either the TNM system or the Enneking system.

TNM is an acronym, where each letter already stands for a particular stage of cancer. The first stage is T, for Tumor, where the size of the tumor is taken into consideration. The earliest stage may not show any indication that a tumor exists, the next development, called T1, is for when the tumor has grown up to eight centimeters/three inches. T3 will show manifestations of tumor cells in other areas of the bone, but not outside it just yet.

Stage 2 of bone cancer under the TNM system is N, for lymph nodes, meaning the cancer has extended to the lymph nodes. M, the third stage, is metastasization, or the spreading of the cancer to other areas or other parts of the body.

The Enneking system is used primarily for bone cancer staging, taking into consideration histological subtype, whether or not the cancer is still inside the bone and the grade at which the cancer is advancing. Bone cancer cells have two grades, which can be determined by examining cancerous tissue under a microscope. Low grade cells are those that are already cancerous but do not appear differently from normal cells. High grade cancer cells not only appear abnormal but also grow much quicker than low grade tumors.

The Enneking staging system is different from TNM system as the N or lymph node stage is placed not under the second stage, but under stage 3. The first and second stages of bone cancer under the Enneking system have not spread at all, not even to the lymph nodes, and are differentiated according to grade. Stage 1 is low grade, stage 2 is high grade.

Each stage under the Enneking system is further divided, according this time to the location of the cancer. Stage 1A is low grade cancer that has remained inside the bone. This is called intra compartmental bone cancer, with the “compartment” being the bone wall. Stage 1A cancer is not so far gone that it will require chemotherapy; it may be treated by surgery, instead.

Stage 1B cancer is still low grade cancer but has stretched out through the wall of the bone, or outside its “compartment.” This is now called extra compartmental.

Stage 2A cancer is already high grade cancer within the bone, or intra compartmental. Meanwhile Stage 2B cancers have grown outside the compartment and are extra compartmental. In both stages 1 and 2 of extra compartmental cancer, the cancerous cells have not spread far from the bone. They have only grown out of the bone wall and remain in the tissues found right outside the bone. Chemotherapy is now applied in the second stage of cancer, as high grade cancer cells develop quicker and will spread further.

Stage 3 will see the cancer spreading to the lymph nodes, and onward to other organs and tissue. Bone cancer usually spreads quickly to the lungs at this stage.

An integration of the TNM and Enneking systems into one improved system is currently being developed.

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