The grading system is divided into four grades based on the degree of cell differentiation:
Grade I: Well-differentiated tumors with cells that closely resemble normal tissue. These tumors are generally less aggressive. Grade II: Moderately differentiated tumors with cells that appear somewhat abnormal and less like the original tissue. Grade III: Poorly differentiated tumors with cells that look very different from normal tissue and have a higher degree of abnormality. Grade IV: Undifferentiated or anaplastic tumors with cells that have lost all resemblance to the original tissue. These are the most aggressive tumors.
