The standardized procedure for expressing cancer cell differentiation, called grading, and the extent of dissemination of the cancer, called staging. This procedure is very helpful in comparing the results of various forms of therapy. Cancer is graded on the differentiation of the tumor cells and the number of mitoses present. These are thought to be correlated with the ability of the tumor to grow and spread. Some cancers are graded I to IV, the latter being the most anaplastic and having the least resemblance to normal tissue.