TNM system for oral cancer
We stage oral cancer using The American Joint Committee on Cancer’s (AJCC) TNM system, a commonly accepted method based on three key components:
- Tumor (T) describes the size of the original tumor.
- Node (N) indicates whether the cancer is present in the lymph nodes.
- Metastasis (M) refers to whether cancer has spread to other parts of the body.
A number (0-4) or the letter X is assigned to each factor. A higher number indicates increasing severity. For instance, a T1 score indicates a smaller tumor than a T2 score. The letter X means the information could not be assessed.
Once the T, N, and M scores have been assigned, an overall stage is assigned.
T Categories for Oral Cavity and Oropharyngeal Cancers
These measurements refer to the primary oral cancer tumor.
TX: primary tumor cannot be assessed; information not known.
TO: no evidence of primary tumor Tis: carcinoma in situ. This means that the disease is still localized, or contained within the top layers of cells lining the oral cavity and oropharynx. Cancer cells have not invaded the deeper layers of oral or oropharyngeal tissue.
T1: tumor is 2 cm across or smaller.
T2: tumor is larger than 2 cm across, but smaller than 4 cm.
T3: tumor is larger than 4 cm across.
T4 is divided into two subgroups:
- T4a: the tumor is growing into nearby structures. At this stage, the oral cancer is called a moderately advanced local disease. The areas to which cells have spread vary according to the type of oral cancer:
- For oral cavity cancers: the tumor is growing into nearby structures such as the bones of the jaw or face, deep muscle of the tongue, skin of the face, or maxillary sinus.
- For lip cancers: the tumor is growing into nearby bone, the inferior alveolar nerve (the nerve to the jawbone), the floor of the mouth, or the skin of the chin or nose.
- For oropharyngeal cancers: the tumor is growing into the larynx (voicebox), the tongue muscle, or bones such as the hard palate or jaw.
- T4b: the tumor has grown through nearby structures and into deeper areas or tissues. At this stage, the cancer is called very advanced local disease, and may include any of the following conditions:
- The tumor is growing into other bones, such as the pterygoid plates (in the skull) and/or the skull base. This type of spreading can occur with any oropharyngeal or oral cancer.
- The tumor surrounds the internal carotid artery. This type of spreading can occur with any oropharyngeal or oral cancer.
- For lip and oral cavity cancers: the tumor is growing into an area called the masticator space
- For oropharyngeal cancers: the tumor is growing into a muscle called the lateral pterygoid muscle, which is used for chewing.
- For oropharyngeal cancers: the tumor is growing into the nasopharynx (the area of the throat that is behind the nose).
N Categories for Oral Cavity and Oropharyngeal Cancers
NX: nearby lymph nodes cannot be assessed; information not known.
N0: the oral cancer has not spread to any nearby lymph nodes.
N1: the cancer has spread to one lymph node on the same side of the head or neck as the primary tumor. This lymph node is smaller than 3 cm across.
N2 is divided into three subgroups:
- N2a: the oral cancer has spread to one lymph node on the same side as the primary tumor, and the lymph node measures 3–6 cm across.
- N2b: the cancer has spread to 2 or more lymph nodes on the same side as the primary tumor. No lymph nodes are larger than 6 cm across.
- N2c: the oral cancer has spread to one or more lymph nodes on both sides of the neck or on the side opposite the primary tumor. No lymph nodes are larger than 6 cm across.
- N3: the cancer has spread to a lymph node that measures more than 6 cm across.
M Categories for Oral Cavity and Oropharyngeal Cancers
M0: no distant spread.
M1: the oral cancer has spread to distant sites outside the head and neck region (for example, the lungs, liver or bones).