Sarcoma

Staging

Staging is how doctors determine the extent of your sarcoma, where it is located and whether it has metastasized (spread) to nearby organs, tissues or lymph nodes, or to other parts of your body. The stage also assists in determining the prognosis (outlook) for the disease. The grade can indicate growth rate. Your doctor will consider the results of your physical examination, imaging studies, blood tests and a biopsy of the tumor. However, additional tests may be needed.

Your doctor will order various studies, which may include X-rays, CT (computed tomography), magnetic resonance imaging (MRI) and nuclear medicine (bone scans), which will assist in completing the staging of your cancer.

Your doctor may also suggest molecular laboratory tests on a tumor sample (after it is biopsied or removed) to identify specific genes, proteins and other factors unique to the tumor, including its molecular characteristics. Ask your doctor if the tissue samples from other tests you’ve had can be used for molecular testing to prevent additional procedures, if possible.

Because of the many subtypes of sarcoma, staging may be challenging. Your surgeon may present your case at a multidisciplinary sarcoma tumor board, which is a meeting of a group of physicians involved with sarcoma treatment. This team consists of many physicians “behind the scenes” but deeply involved in your care, such as sarcoma pathologists, musculoskeletal radiologists, pediatric and adult oncologists, radiation oncologists, rehabilitation physicians, and nonphysician personnel such as social workers, tumor registrars and chaplains. This team will discuss and evaluate your case in great detail and arrive at decisions best suited to you personally.

This is also a good time to get a second opinion from another sarcoma specialist. A second opinion will confirm the diagnosis and recommended treatment plan or introduce new information to consider.

Staging Soft Tissue Sarcomas

The staging and grading system most commonly used for soft tissue sarcomas is the American Joint Committee on Cancer (AJCC) TNM staging system. Soft tissue sarcomas are staged and graded based on where they are found in the body, including soft tissues of the head and neck, trunk and extremities, abdomen and thoracic visceral organs and the retroperitoneum (the space behind the lining of the abdomen).

TNM staging uses the tumor (T), node (N) and metastasis (M) classification system, which takes into account the tumor’s size and location, whether cancer cells are in nearby lymph nodes and if it has metastasized to other parts of the body. Soft tissue sarcomas commonly spread to the lungs. Numbers after T, N and M provide more details for each of these factors.

For both bone and soft tissue sarcomas, a grade (G) is given to indicate how rapidly the sarcoma will grow and spread. Knowing the grade will also help determine the prognosis (predicted outcome). The pathologist will examine sarcoma cells through a microscope and then assign a number to the grade according to how different these cells are from normal tissue cells, the number of tumor cells dividing and how much of the tumor has cells that are dying.

Grades range from low to high as GX (grade cannot be assessed), Grade 1 (G1), Grade 2 (G2) and Grade 3 (G3). Healthy cells are called well-differentiated (indicated by a lower grade). Low-grade tumor cells look more like normal cells and are less likely to grow and spread quickly. High-grade tumor cells (poorly differentiated cells) look more abnormal and tend to grow and spread faster. In general, the more differentiated the tumor, the better the prognosis.

The information your doctor gathers about the tumor, lymph nodes, possible metastasis and grade is used to assign a stage through a process called stage grouping. Roman numerals I to IV indicate the stages. Stage grouping is used for soft tissue sarcomas of the trunk and extremities (see Table 3) and retroperitoneum (see Table 4). However, stage grouping is currently unavailable for soft tissue sarcomas of the head and neck (see Table 1) and the abdomen and thoracic visceral organs (see Table 2) because more data is needed to offer any prognostic value.

Table 1. Soft Tissue Sarcoma of the Head & Neck

Classification Definition
Tumor (T)
TX Primary tumor cannot be assessed.
T1 Tumor 2 cm (almost 1 inch) or less.
T2 Tumor more than 2 cm but not more than 4 cm (about 1 ½ inches).
T3 Tumor more than 4 cm.
T4
  T4a


  T4b
Tumor with invasion of adjoining structures.
Tumor with orbital invasion, skull base/dural invasion, invasion of central compartment viscera, involvement of facial skeleton or invasion of pterygoid muscles.
Tumor with brain parenchymal invasion, carotid artery encasement, prevertebral muscle invasion, or central nervous system involvement via perineural spread.
Node (N)
N0 No regional lymph node metastases or unknown lymph node status.
N1 Regional lymph node metastasis.
Metastasis (M)
M0 No distant metastasis.
M1 Distant metastasis.

 

Grade (G) Definition
GX Grade cannot be assessed.
G1 Total differentiation, mitotic count and necrosis score of 2 or 3.
G2 Total differentiation, mitotic count and necrosis score of 4 or 5.
G3 Total differentiation, mitotic count and necrosis score of 6, 7 or 8.

 

Table 2. Soft Tissue Sarcoma of the Abdominal and Thoracic Visceral Organs

Classification Definition
Tumor (T)
TX Primary tumor cannot be assessed.
T1 Organ confined.
T2
  T2a
  T2b
Tumor extension into tissue beyond organ.
Invades serosa or visceral peritoneum.
Extension beyond serosa (mesentery).
T3 Invades another organ.
T4
  T4a
  T4b
  T4c
Multifocal involvement (tumors at more than 1 site).
Multifocal (2 sites).
Multifocal (3-5 sites).
Multifocal (more than 5 sites).
Node (N)
N0 No lymph node involvement or unknown lymph node status.
N1 Lymph node involvement present.
Metastasis (M)
M0 No metastasis.
M1 Metastases present.

 

Grade (G) Definition
GX Grade cannot be assessed.
G1 Total differentiation, mitotic count and necrosis score of 2 or 3.
G2 Total differentiation, mitotic count and necrosis score of 4 or 5.
G3 Total differentiation, mitotic count and necrosis score of 6, 7 or 8.

 

Table 3. Soft Tissue Sarcoma of the Trunk & Extremities

Classification Definition
Tumor (T)
TX Primary tumor cannot be assessed.
T0 No evidence of primary tumor.
T1 Tumor 5 cm (almost 2 inches) or less in greatest dimension.
T2 Tumor more than 5 cm and less than or equal to 10 cm (almost 4 inches) in greatest dimension.
T3 Tumor more than 10 cm and less than or equal to 15 cm (approximately 6 inches) in greatest dimension.
T4 Tumor more than 10 cm and less than or equal to 15 cm (approximately 6 inches) in greatest dimension.
Node (N)
N0 No regional lymph node metastasis or unknown lymph node status.
N1 Regional lymph node metastasis.
Metastasis (M)
M0 No distant metastasis.
M1 Distant metastasis.

 

Grade (G) Definition
GX Grade cannot be assessed.
G1 Total differentiation, mitotic count and necrosis score of 2 or 3.
G2 Total differentiation, mitotic count and necrosis score of 4 or 5.
G3 Total differentiation, mitotic count and necrosis score of 6, 7 or 8.

 

Stage T N M G
IA T1 N0 M0 GX, G1
IB T2, T3, T4 N0 M0 GX, G1
II T1 N0 M0 G2, G3
IIIA T2 N0 M0 G2, G3
IIIB T3, T4 N0 M0 G2, G3
IV
Any T
Any T
N1
Any N
M0
M1
Any G
Any G

 

Table 4. Soft Tissue Sarcoma of the Retroperitoneum

Classification Definition
Tumor (T)
TX Primary tumor cannot be assessed.
T0 No evidence of primary tumor.
T1 Tumor 5 cm (almost 2 inches) or less in greatest dimension.
T2 Tumor more than 5 cm and less than or equal to 10 cm (almost 4 inches) in greatest dimension.
T3 Tumor more than 10 cm and less than or equal to 15 cm (approximately 6 inches) in greatest dimension.
T4 Tumor more than 15 cm in greatest dimension.
Node (N)
N0 No regional lymph node metastasis or unknown lymph node status.
N1 Regional lymph node metastasis.
Metastasis (M)
M0 No distant metastasis.
M1 Distant metastasis.

 

Grade (G) Definition
GX Grade cannot be assessed.
G1 Total differentiation, mitotic count and necrosis score of 2 or 3.
G2 Total differentiation, mitotic count and necrosis score of 4 or 5.
G3 Total differentiation, mitotic count and necrosis score of 6, 7 or 8.

 

Stage T N M G
IA T1 N0 M0 GX, G1
IB T2, T3, T4 N0 M0 GX, G1
II T1 N0 M0 G2, G3
IIIA T2 N0 M0 G2, G3
IIIB
T3, T4
Any T
N0
N1
M0
M0
G2, G3
Any G
IV Any T Any N M1 Any G

Used with permission of the American Joint Committee on Cancer (AJCC), Chicago, Illinois. The original and primary source for this information is the AJCC Cancer Staging Manual, Eighth Edition (2017) published by Springer Science+Business Media.

Staging Bone Sarcomas

When doctors stage bone sarcomas, they use many of the same tests used for soft tissue sarcomas. They will also determine if the tumor is localized (seen only in the bone it started in and possibly tissues next to the bone, such as muscle, tendon or fat), or metastatic (has spread to other parts of the body). Depending on the type of bone sarcoma, one of two preferred staging systems will be used.

AJCC’s TNM staging system considers the size and location of the tumor (T), whether cancer cells are found in nearby lymph nodes (N) and whether the cancer has metastasized (M) to other parts of the body. It also includes a grading system (GX-G3), which indicates the tumor’s aggressiveness. Stages are indicated by Roman numerals I to IV.

The Musculoskeletal Tumor Society (MSTS) staging system, also known as the Enneking system, is based on the grade (G) of the tumor, the extent of the main (primary) tumor (T) and whether the tumor has metastasized (M) to nearby lymph nodes or other organs.

In the MSTS system, bone sarcomas are staged by how likely the tumor is to grow and spread (G1 or G2), whether the tumor has remained inside the bone (T1) or extended beyond the bone (T2), and if the tumor has spread to other organs (M1). Combining these factors gives an overall stage, which is indicated by Roman numerals I to III.

Additional Resources

 

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