The measurement of a cancer reflecting how abnormal the cells look under a microscope. There are several grading systems for cancer, but all divide cancers into those with the greatest abnormality (grade 3 or poorly differentiated), the least abnormality (grade1 or well differentiated) and intermediate features (grade 2 or moderately differentiated). Grading is done by the pathologist who examines the biopsy specimen. It is important because higher grade cancers tend to grow and spread more quickly and have a worse prognosis. A cancer's nuclear grade is based on features of the central part of its cells, the nucleus. The histologic grade is based on features of individual cells as well as how the cells are arranged together.