The TNM staging of oral cancer is the most used classification in the world. It is widely applied as the main classification system for reporting this disease. 

Т describes the size and depth of the tumor:

TX – Main tumor cannot be measured;

Тis – Carcinoma in situ;

Т1 means the cancer is contained within the tissue of the mouth (oral cavity) and it is:

• 2 cm or smaller;
• 5 mm deep or less;

Т2 can mean different things:

• The cancer is 2 cm or smaller, and it is deeper than 5 mm but no deeper than 10 mm;    
• Or the cancer is larger than 2 cm, but no larger than 4 cm, and it is 10 mm deep or less;

T3 means:

• The cancer is larger than 4 cm, or deeper than 10 cm;

Т4 се разделя на 2 групи:

T4a – means the cancer has grown further than the mouth and into surrounding structures such as bone, skin or the facial air cavities (sinuses);

T4b – means the cancer has spread into nearby areas such as the space behind the jaw, the base of the skull, or the area of neck surrounding the arteries (carotid arteries);

N refers to the involved lymph nodes:

N0 – means the lymph nodes don’t contain cancer cells;

N1 – means that one lymph node contains cancer cells on the same side of the neck as the cancer. The node is no larger than 3 cm across. The cancer has not spread into tissue surrounding the lymph node;

N2 is split into 3 groups:

N2a – means one lymph node contains cancer cells on the same side of the neck as the cancer. The node is between 3 cm and 6 cm across. The cancer has not spread into tissue surrounding the lymph node;

N2b – means that more than one lymph node contain cancer cells on the same side of the neck as the cancer. None of these nodes are more than 6 cm across. The cancer has not spread into tissue surrounding the lymph node;

N2c – means there are cancer cells in lymph nodes on the other side of the neck to the cancer, or in nodes on both sides of the neck. None of these nodes are more than 6 cm across. The cancer has not spread into tissue surrounding the lymph node;

N3 is split into 2 groups:

N3a – means that one lymph node that contains cancer cell is larger than 6 cm across. The cancer has not spread into tissues surrounding the lymph node;

N3b – means any number of lymph nodes contain cancer. The cancer has spread into tissues surrounding the lymph node;

М describes whether the cancer has spread to a different part of the body. There are 2 main stages - M0 and M1:

M0 – means the cancer has not spread to other parts of the body;

М1 – means cancer has spread to other parts of the body such as the lungs;