In the stage IIA of the cancer, the cancerous cells spread from the muscle layer to the outermost layer (known as serosa) of the colon or the rectum wall.
Stage IIB is characterized by the proliferation of the cancerous cells beyond the serosa but these cells have not impregnated the nearby organs of the individual.
Stage IIC marks the proliferation of cancerous cells to the nearby organs of an individual as they move beyond the serosa.

Stage III: The stage III of colorectal cancer is further classified into stages IIIA, IIIB, and IIIC.

Stage IIIA marks the spread of cancerous cells to at least one but less than four lymph nodes that are in the periphery of the colon or rectum serosa. This stage also marks the formation of cancer cells in the tissues surrounding the lymph nodes. The stage IIIA of colorectal cancer can also signify the proliferation of cancerous cells beyond the inner most layer (instead of the outermost layer) of the colon or the rectum. The cancerous cells can then spread to 4-6 lymph nodes in close vicinity of the colon.

Stage IIIB is characterized by the proliferation of cancerous cells in 7 or more lymph nodes near the colon.
Stage III C of bowel cancer represents the spread of cancerous cells to the nearby organs, or the formation of cancerous cells near the lymph nodes.

Stage IV: Stage IV of colorectal cancer signifies the spread of cancer cells to nearby lymph nodes or organs. With an advancement of this stage, cancerous cells might start forming in one or more organs that are not near the colon, for instance, the lungs, liver, or the ovary.
Determining colon cancer stages in an individual is critical for establishing the best treatment plan.