Staging of Ewing Sarcoma

Once Ewing sarcoma has been diagnosed, other tests are done to determine the stage (extent) of the cancer. The stage of Ewing sarcoma describes how much cancer is in the body.

Staging systems for Ewing sarcoma

A staging system is a standard way for the cancer care team to sum up the extent of the cancer. Different types of cancers have different staging systems.

The stage is based on results of imaging tests and biopsies of the main tumor and any other body tissues.

Doctors are most likely to describe Ewing sarcoma using a simple, informal system. This system classifies Ewing sarcoma tumors as localized or metastatic.

The formal (and more detailed) staging systems for bone and soft tissue tumors are the American Joint Committee on Cancer (AJCC) systems for bone cancers and soft tissue sarcomas and the Musculoskeletal Tumor Society (MSTS) staging systems. These aren’t used often but are described briefly below to help you understand them in case your doctor refers to one of them.

Localized Ewing sarcoma

Ewing sarcoma is localized if it can only be detected in the area where it started or in nearby tissues such as muscle or tendons.

Ewing sarcoma can only be called localized after all tests have been done (including imaging tests, PET or bone scans, and possibly a bone marrow biopsy), and they don't show the cancer has spread to distant parts of the body.

Even when imaging tests don't show that the cancer has spread to distant areas, most patients are likely to have micrometastases (very small areas of cancer spread that can’t be detected with tests). This is why chemotherapy, which can reach all parts of the body, is an important part of treatment for all Ewing sarcoma.

Metastatic Ewing sarcoma

Metastatic Ewing sarcoma has spread from where it started to distant areas of the body. Most of the time, it spreads to the lungs, other bones, or the bone marrow. Less commonly, it spreads to the liver or lymph nodes.

About 1 in 5 patients will have obvious spread that is found by imaging tests. But as mentioned above, many other patients are likely to have small amounts of cancer metastasis that can’t be seen on imaging tests.

Other bone sarcoma staging systems

While not typically used for staging and treatment planning of Ewing sarcoma, you may hear of the AJCC TNM staging system. This system, which is common for other types of cancer, describes tumor characteristics, the extent of spread to lymph nodes (which is rare in bone sarcomas), whether the cancer has metastasized (spread) to other organs, and the grade or appearance of the cancer cells under a microscope.

This information together is used to assign a tumor stage. The stage is represented by a roman numeral I-IV, and is sometimes divided further.

Another system of staging bone tumors is called the MSTS or Enneking staging system. This system similarly uses the location, whether or not a tumor has spread, and its appearance under the microscope to describe a tumor stage using Roman numerals from I to III. Stages I and II are divided into A for intra-compartmental tumors (tumors that stay in one place) or B for extra-compartmental tumors (tumors that spread to surrounding areas).

For more information see Bone Cancer Stages.