Debra
Here is a link to the OCF main web page that spells out all the staging definitions OCF-staging explanation
If you have a slow internet connection: here is an excerpt

[quote]T4 (Oral cavity) Tumor invades adjacent structures (e.g., through cortical bone, into deep [extrinsic] muscle of tongue, maxillary sinus, skin)
N0 No regional lymph node metastasis
M0 No distant metastasis
Stage IV
Any of the following may be true: The cancer has spread to tissues around the lip and oral cavity. The lymph nodes in the area may or may not contain cancer. The cancer is any size and has spread to more than one lymph node on the same side of the neck as the cancer, to lymph nodes on one or both sides of the neck, or to any lymph node that measures more than 6 centimeters (over 2 inches). The cancer has spread to other parts of the body.
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Charm