Once the type of cancer is determined, the pathologist (a doctor who studies the biology of tumors), will look further into the cells to determine the grade of the tumor. The grade of the tumor is an indication of how aggressively the cells might behave. Pathologists grade the tumors from 1 to 3, with the higher number being the worst prognosis. They also look to see if there are cells in the middle of a blood vessel or lymph vessel. This helps them determine how well behaved a cell is in the tissue. The pathologist looks at the margins of the tissue by putting ink around the outside of the sample, so she can measure the amount of normal tissue between the edge of the specimen and the cancer tissue. This is called the tumor margin.

If cancer is only on the inside and not beyond the ink drawn by the pathologist, then it is referred to as having a clear margin or a negative margin (a sign that no obvious cancer was left behind in that area). A positive margin means that cancer cells are found at the outer edge of the removed sample and is usually a sign that some cancer may still be present in the body. This still is an educated guess and the doctors can't be 100 percent sure. When there are questions, seeking a second opinion is advised.