Grading and Staging of Cancer
What is grading of cancer?
Histologic "grade" is sometimes to used to describe what a cancer looks like microscopically.
Most cancers are graded by how much they look like normal cells. Well-differentiated
(low grade or grade I) tumors look more like normal tissue. Poorly differentiated
(high grade or grade III) tumors look disorganized under the microscope and may behave
more aggressively than grade I tumors. Those tumors that look neither well-differentiated
nor poorly differentiated are designated moderately differentiated, or grade II. The
histologic grade can suggest how slow growing (grade I) or aggressive (grade III)
a tumor is.
What is staging of cancer?
Once cancer is diagnosed, more tests will be done to find out the size of the tumor
and whether the cancer cells have spread to other parts of the body. This testing
is called staging. To plan treatment, a healthcare provider needs to know the stage
of the disease. Stage refers to the extent, or the size, of the cancer and whether
it has spread from where it started. Each cancer, by organ, has its own staging system.
In most cases, the stage is labeled with 0 and Roman numerals I through IV, with stage
IV being the most advanced stage.
Stages of cancer (the following list is general; each tumor type has its own [and
sometimes, complex] staging system)
Stage 0 or carcinoma in situ. Carcinoma in situ is very early cancer. The abnormal cells are found only in the first
layer of cells of the primary site and do not invade the deeper tissues. This stage
is referred to as pre-malignant or pre-cancerous.
Stage I. Cancer involves the primary site, and is considered early stage and most curable.
Stage II. Cancer involves the primary site. It may be a bit larger than stage I disease or involve
nearby lymph nodes.
Stage III. Cancer involves the primary site and involves nearby lymph nodes.
Stage IV. Cancer has spread to other parts of the body (metastasized).
Recurrent. Recurrent disease means that the 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 in which it first developed. Once a stage is assigned
and treatment given, the stage is never changed. For example, if a stage I cancer
of the cervix is treated, and 2 years later a metastasis (spread of the same cancer)
is found in the lung, it is not now stage IV, but remains a 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