The stage and grade of a cancer are ways to measure how severe the disease is. Tumors are described by their size, whether they have spread, and how their cells look under a microscope.

There are three parts to staging:

• Tumor size (T)
• Involvement of lymph nodes (N)
• Whether the tumor has spread (metastasized) from the original site to other parts of the body (M)

This staging system is commonly referred to as the TNM cancer staging system. Some cancers, such as lymphomas, have a different staging system. Most leukemias don't have a staging system.

Tumor grading describes how tumor cells look under a microscope. Tumor cells that look like normal cells (well-differentiated) are called Grade 1 tumors. They usually grow slowly. Cells that look very different from normal cells are said to be undifferentiated (Grade 4). These cells often grow quickly and spread rapidly.

The following system may be used to grade tumors:

• Grade cannot be assessed (GX)
• Well-differentiated (G1)
• Moderately differentiated (G2)
• Poorly differentiated (G3)
• Undifferentiated (G4)

This is a general grading system. Some cancers, such as prostate cancer and bladder cancer, have their own grading systems.