What is the defining feature of a grade 4 tumor?

A grade 4 tumor is characterized by its undifferentiated nature, meaning that the cancer cells appear very abnormal and do not resemble the original tissue from which they originated. This indicates a high level of aggressiveness and malignancy. Tumors are graded based on how much the cancer cells differ from normal cells; as the grade increases, the cells tend to show less resemblance to their tissue of origin. In the case of grade 4 tumors, the significant degree of undifferentiation points to a worsening prognosis and often suggests a tendency to grow and spread more rapidly than lower-grade tumors. This feature is critical in determining treatment strategies and potential outcomes for the patient, highlighting the importance of tumor grading in oncology.