After cancer is diagnosed, healthcare providers will begin to determine the grade and stage of the cancer. This helps them to plan the best treatment and look at overall outcomes and goals.
The grade of a cancer describes what the cancer cells look like using a microscope. Most cancers are graded by how they compare with normal cells. Low grade or grade I tumors are well-differentiated. This means that the tumor cells are organized and look more like normal tissue. High grade or grade III tumor cells are poorly differentiated. This means that the tumor cells don't look like normal cells. They're disorganized under the microscope and tend to grow and spread faster than grade I tumors. Cancer cells that don't look well-differentiated or poorly differentiated are called moderately differentiated, or grade II. In general, cancer cells are graded using the scale below. (Be aware that some may use grade 3 as the highest grade):
Grade X. Grade isn't known
Grade 1. Well differentiated, low grade
Grade 2. Moderately differentiated, intermediate grade
Grade 3. Poorly differentiated, high grade
Grade 4. Undifferentiated, high grade
Once cancer is diagnosed, you will need more exams and tests to find out how much cancer is in your body and where it is. These exams and test will also help tell if the cancer has grown into nearby areas and if it has spread to other parts of the body. This is called staging. The stage of a cancer is one of the most important things to know when deciding on how to treat the cancer.
Each cancer, by organ, has its own staging system. In most cases, the stages are listed as Roman numerals and can have a value of I through IV (1 to 4). The higher the number, the more advanced the cancer is. Letters and numbers can be used after the Roman numeral to give more details.
Depending on your type of cancer, you may hear about the TNM system to describe the stage. TNM isn't used to stage all types of cancers. T describes the original tumor and how deep into nearby tissue it has spread. N describes if the cancer has spread to nearby lymph nodes. M describes if the cancer has spread, or metastasized, to other areas of the body.
Each type of cancer tumor has its own, often complex, staging system. The following is a general list of stages of cancer:
Stage 0 or carcinoma in situ. Carcinoma in situ is considered pre-malignant or pre-cancer. Abnormal cells are found only in the first layer of cells in the place where the changes first started. The cells do not invade the deeper tissues. These cells may become cancer over time, so it's good to find and treat them before that happens. Most kinds of cancer do not use this stage.
Stage I. Cancer is only in the cells where it first started and the area is small. This is considered early stage and most curable.
Stage II. Cancer is in the organ where it first started. It may be a bit larger than stage I and/or may have spread to nearby lymph nodes.
Stage III. Cancer in the organ where it first started. It may be larger than stage II and may have spread to nearby lymph nodes and/or other nearby tissues, organs, or structures.
Stage IV. Cancer has spread to organs in other parts of the body ( metastasized). There may be cancer in different organs, but it's still the same type of cancer as where it first started. For instance, colon cancer that spreads to the liver is not liver cancer, it's stage IV colon cancer with liver metastasis. The cancer cells in the liver look like the cancer cells in the colon and are treated like colon cancer.
Recurrent. Recurrent cancer has come back (recurred) after it has been treated. It may come back in the same area or in a different part of the body.
Higher numbers usually mean more extensive disease, larger tumor size, and/or spread of the cancer beyond the organ where it first developed. Higher grade and stage cancers tend to be harder to cure and often require more intense treatments.
Once a stage is assigned and treatment given, the stage is never changed. For instance, a stage I cancer of the cervix is treated. Two years later, the same cancer has spread and is now found in the lung. It isn't now stage IV, but is still stage I, with recurrence to the lung.
The important thing about staging is that it determines the appropriate treatment, helps healthcare providers make a prognosis, and allows for comparison of treatment results.
Cancer grade and stage can be very complex and confusing. Ask your healthcare provider to explain these details about your cancer to you in a way you can understand. Consider bringing a friend or family member to your visits to help support you.