How are soft tissue sarcomas staged?
The process of finding out how far the cancer has spread is called staging. In sarcoma staging, doctors also evaluate the appearance of the tumor under the microscope and judge how fast the cancer seems to be growing. The stage of a sarcoma is the most significant factor in determining each patient's prognosis (the course of the disease and the chances of survival) and in selecting treatment options.
The information needed to stage sarcomas includes biopsies, and imaging tests of the main tumor (usually with CT or MRI scans) other parts of the body where the cancer may have spread.
When examining the biopsy sample, the pathologist (doctor who specializes in diagnosing diseases by looking at the tissue under a microscope) takes into account the number of cells that are actively dividing and how closely the cancer resembles normal tissue. He or she determines the cell type and grade and estimates how rapidly it will grow and spread.
A staging system is a standard way for the cancer care team to summarize the extent of a cancer's spread. The system often used to stage sarcomas is the TNM system of American Joint Committee on Cancer.
- T stands for the size of the tumor.
- N stands for spread to lymph nodes (small bean-shaped collections of immune system cells found throughout the body that help fight infections and cancers).
- M is for metastasis (spread to distant organs).
In soft tissue sarcomas, an additional factor, called grade (G), is also part of the tumor’s stage. The grade is based on how the sarcoma cells look under the microscope.
The grade is a sign of how likely it is the cancer will spread. Previously, the grade of a sarcoma was only based on how normal the cells looked under the microscope (called differentiation). This was not very helpful, and under a new system (known as the French or FNCLCC system), grade is based on 3 factors:
- Differentiation — cancer cells are given a score of 1 to 3, with 1 being assigned when they look similar to normal cells and 3 being used when the cancer cells look very abnormal
- Mitotic count — how many cancer cells are seen dividing under the microscope; given a score from 1 to 3 (a lower score means fewer cells were seen dividing)
- Tumor necrosis — how much of the tumor is made up of dying tissue; given a score from 0 to 2 (a lower score means there was less dying tissue present).
The scores for each factor are added to determine the grade for the cancer. Higher-grade cancers tend to grow and spread faster than lower-grade cancers.
GX: the grade cannot be assessed (because of incomplete information).
Grade 1 (G1): Total score of 2 or 3
Grade 2 (G2): Total score of 4 or 5
Grade 3 (G3): Total score of 6 or higher
T1: The sarcoma is 5 cm (2 inches) or less across
- T1a: The tumor is superficial − near the surface of the body.
- T1b: The tumor is deep in the limb or abdomen.
T2: The sarcoma is greater than 5 cm (2 inches) across.
- T2a: The tumor is superficial − near the surface of the body.
- T2b: The tumor is deep in the limb or abdomen.
Lymph nodes (N)
N0: The sarcoma has not spread to nearby lymph nodes.
N1: The sarcoma has spread to nearby lymph nodes.
M0: No distant metastases (spread) of sarcoma are found.
M1: The sarcoma has spread to distant organs or tissues (such as the lungs).
Stage grouping for soft tissue sarcomas
To assign a stage, information about the tumor, its grade, lymph nodes, and metastasis is combined by a process called stage grouping. The stage is described by Roman numerals from I to IV and the letters A or B. The stage is useful in selecting treatment, but other factors, such as where the sarcoma is located, also influence treatment planning and outlook.
T1, N0, M0, G1 or GX: The tumor is not larger than 5 cm (2 inches) across (T1). It has not spread to lymph nodes (N0) or more distant sites (M0). The cancer is grade 1 (or the grade cannot be assessed).
T2, N0, M0, G1 or GX: The tumor is larger than 5 cm (2 inches) across (T2). It has not spread to lymph nodes (N0) or more distant sites (M0). The cancer is grade 1 (or the grade cannot be assessed).
T1, N0, M0, G2 or G3: The tumor is not larger than 5 cm (2 inches) across (T1). It has not spread to lymph nodes (N0) or more distant sites (M0). The cancer is grade 2 or 3.
T2, N0, M0, G2: The tumor is larger than 5 cm (2 inches) across (T2). It has not spread to lymph nodes (N0) or more distant sites (M0). The cancer is grade 2.
T2, N0, M0, G3: It is larger than 5 cm (2 inches) across (T2). It has not spread to lymph nodes (N0) or more distant sites (M0). The cancer is grade 3.
Any T, N1, M0, any G: The cancer can be any size (any T) and any grade. It has spread to nearby lymph nodes (N1). It has not spread to distant sites (M0).
Last Medical Review: 10/21/2013
Last Revised: 02/06/2014