In grade 4 cancer, tumor cells look very different from the normal cells, and most likely, they have spread to distant organs. Such tumors have a poorer outlook and may need more aggressive management. Usually, tumors in grade 4 are undifferentiated and very aggressive. However, the grading criteria vary in tumors in different organs and different types of tumors.
Grading describes how the cancer cells look compared to normal, healthy cells. Knowing cancer grade helps doctors predict how fast cancer may grow and how likely is it to spread. The grade is usually described using a number from one to three or four. The higher the number, the more different the cancer cells look from healthy cells and the faster they are growing:
- GX: In this grade, the tumor may not be assessed yet, hence considered to be an undetermined grade.
- G1: In this grade, the tumor may be well-differentiated and is considered low grade. Tumor cells and tissue look mostly like healthy cells and tissue.
- G2: Tumor may be moderately differentiated, and it is called intermediate grade. The cells and tissue are somewhat abnormal.
- G3: Tumors are poorly differentiated and are considered high grade. Cancer cells and tissue look very abnormal.
- G4: These undifferentiated cancers have the most abnormal looking cells. These are the highest grade and typically grow and spread faster than lower grade tumors.
What is the difference between tumor staging and tumor grading?
- Tumor grading: Tumor grade is the description of a tumor based on how abnormal the tumor cells and tissue look under a microscope. It is an indicator of how quickly a tumor is likely to grow and spread.
- Tumor staging: Cancer stage refers to the size and/or extent (reach) of the original (primary) tumor and whether cancer cells have spread in the body. The cancer stage is based on factors, such as the location of the primary tumor, tumor size, regional lymph node involvement (the spread of cancer to nearby lymph nodes), and the number of tumors present.
What are the different types of cancer staging?
There are several different staging systems:
Stage 0 to Stage IV: The most common system that many people are aware of puts cancer on a scale of 0 to IV.
- Stage 0: Cells are abnormal, but they did not spread yet. They may become aggressive in the future. This stage is also called “in-situ.”
- Stage I to Stage III: Cancers have not spread beyond the primary tumor site or have only spread to the nearby tissue. The higher the stage number, the larger the tumor, and the more it has spread.
- Stage IV: Cancer is aggressive and has spread to distant areas of the body.
- Recurrent: Cancer has come back (recurred) after it has been treated. It may come back in the same area or a different part of the body.
Primary tumor (T):
- TX: The main tumor cannot be measured.
- T0: The main tumor cannot be found.
- T in situ: The tumor is still within the confines of the normal glands and cannot metastasize.
- T1, T2, T3, and T4: It refers to the size and/or extent of the main tumor. The higher the number after the T, the larger the tumor or the more it has grown into the nearby tissues. T's may be further divided to provide more detail, such as T3a and T3b, depending on different cancer types.
Regional lymph nodes (N): Lymph nodes are small bean-shaped structures that help move lymph fluid. Cancer often first spreads to and through nearby lymph nodes.
- NX: Cancer in nearby lymph nodes cannot be measured.
- N0: There is no cancer in nearby lymph nodes.
- N1, N2, and N3: It refers to the number and location of lymph nodes that contain cancer. The higher the number after the N, the more the lymph nodes that contain cancer.
Distant metastasis (M): Metastasis is the spread of cancer to other parts of the body.
- MX: Metastasis cannot be measured.
- M0: Cancer has not spread to other parts of the body.
- M1: Cancer has spread to other parts of the body.