Ewing Tumor Stages

Once a Ewing tumor (Ewing sarcoma) has been diagnosed, tests are done to determine the stage (extent) of the cancer. The stage of a Ewing tumor describes how much cancer is in the body. It helps determine how serious the cancer is and how best to treat it. Doctors also use a cancer's stage when talking about survival statistics.

The stage is based on results of imaging tests and biopsies of the main tumor and any other body tissues, which are described in Tests for Ewing Tumors. 

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 formal (and more detailed) staging systems for Ewing tumors are the American Joint Committee on Cancer (AJCC) systems for bone cancers and for soft tissue sarcomas. They are described briefly below to help you understand them, in case your doctor refers to one of them.

But for treatment purposes, doctors often use a simpler system, describing Ewing tumors as either localized or metastatic.

Localized vs. metastatic Ewing tumors

When determining how best to treat Ewing tumors, doctors typically classify them as either localized or metastatic.

Localized Ewing tumors

Doctors call a Ewing tumor localized if it can only be detected in the area where it started or in nearby tissues such as muscle or tendons. A Ewing tumor is considered localized only after all tests have been done (including imaging tests such as x-rays, CT or MRI scans, and 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 tumors.

Metastatic Ewing tumors

A metastatic Ewing tumor has clearly spread from where it started to distant parts of the body. Most of the time, it spreads to the lungs or to 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 spread to other parts of the body that can’t be seen on imaging tests.

AJCC staging system for bone cancers

The AJCC uses one system to describe all bone cancers, including Ewing tumors that start in bone.

The AJCC staging system for bone cancers is based on 4 key pieces of information:

• T describes the size of the main (primary) tumor and whether it appears in different areas of the bone.
• N describes the extent of spread to nearby (regional) lymph nodes (small bean-sized collections of immune system cells). Bone tumors rarely spread to the lymph nodes.
• M indicates whether the cancer has metastasized (spread) to other organs of the body. (The most common sites of spread are to the lungs or other bones.)
• G stands for the grade of the tumor, which describes how the cells from biopsy samples look. Low-grade tumor cells look more like normal cells and are less likely to grow and spread quickly, while high-grade tumor cells look more abnormal. (All Ewing tumors are considered high-grade [G3] tumors.)

Once the T, N, M, and G categories have been determined, the information is combined and expressed as an overall stage. The process of assigning a stage number is called stage grouping. The stages are described in Roman numerals from I to IV (1 to 4), and are sometimes divided further. For more detailed information on the AJCC TNM staging system for bone cancers, see Bone Cancer Stages.

AJCC staging system for soft tissue sarcomas

Extraosseous Ewing (EOE) tumors (Ewing tumors that don’t start in bones) are staged like soft tissue sarcomas. The AJCC staging system for soft tissue sarcomas is based on 4 key pieces of information:

• T describes the size of the main (primary) tumor.
• N describes the extent of spread to nearby (regional) lymph nodes (small bean-sized collections of immune system cells).
• M indicates whether the cancer has metastasized (spread) to other organs of the body.
• G stands for the grade of the tumor, which describes how the cells from biopsy samples look. Low-grade tumor cells look more like normal cells and are less likely to grow and spread quickly, while high-grade tumor cells look more abnormal. (All Ewing tumors are considered high-grade [G3] tumors.)

Numbers or letters after T, N, M, and G provide more details about each of these factors.

Once the T, N, M, and G categories have been determined, the information is combined and expressed as an overall stage. The process of assigning a stage number is called stage grouping. The stages are described in Roman numerals from I to IV (1 to 4), and are sometimes divided further. For more information about soft tissue sarcoma staging, see Soft Tissue Sarcoma Stages.

Ewing tumor stages can be confusing, so be sure to ask someone on the health care team if you have any questions about the stage of the cancer.