user: What are the stages of Nasopharyngeal Cancer ?

assistant: Key Points
                    - After nasopharyngeal cancer has been diagnosed, tests are done to find out if cancer cells have spread within the nasopharynx or to other parts of the body.     - There are three ways that cancer spreads in the body.    - Cancer may spread from where it began to other parts of the body.    - The following stages are used for nasopharyngeal cancer:         - Stage 0 (Carcinoma in Situ)     - Stage I     - Stage II     - Stage III     - Stage IV
                
                
                    After nasopharyngeal cancer has been diagnosed, tests are done to find out if cancer cells have spread within the nasopharynx or to other parts of the body.
                    The process used to find out whether cancer has spread within the nasopharynx or to other parts of the body is called staging. The information gathered from the staging process determines the stage of the disease. It is important to know the stage in order to plan treatment. The results of the tests used to diagnose nasopharyngeal cancer are often also used to stage the disease. (See the General Information section.)
                
                
                    There are three ways that cancer spreads in the body.
                    Cancer can spread through tissue, the lymph system, and the blood:         - Tissue. The cancer spreads from where it began by growing into nearby areas.     - Lymph system. The cancer spreads from where it began by getting into the lymph system. The cancer travels through the lymph vessels to other parts of the body.     - Blood. The cancer spreads from where it began by getting into the blood. The cancer travels through the blood vessels to other parts of the body.
                
                
                    Cancer may spread from where it began to other parts of the body.
                    When cancer spreads to another part of the body, it is called metastasis. Cancer cells break away from where they began (the primary tumor) and travel through the lymph system or blood.         - Lymph system. The cancer gets into the lymph system, travels through the lymph vessels, and forms a tumor (metastatic tumor) in another part of the body.    - Blood. The cancer gets into the blood, travels through the blood vessels, and forms a tumor (metastatic tumor) in another part of the body.        The metastatic tumor is the same type of cancer as the primary tumor. For example, if nasopharyngeal cancer spreads to the lung, the cancer cells in the lung are actually nasopharyngeal cancer cells. The disease is metastatic nasopharyngeal cancer, not lung cancer.
                
                
                    The following stages are used for nasopharyngeal cancer:
                    Stage 0 (Carcinoma in Situ)    In stage 0, abnormal cells are found in the lining of the nasopharynx. These abnormal cells may become cancer and spread into nearby normal tissue. Stage 0 is also called carcinoma in situ.       Stage I    In stage I, cancer has formed and the cancer:            - is found in the nasopharynx only; or     - has spread from the nasopharynx to the oropharynx and/or to the nasal cavity.           The oropharynx is the middle part of the throat and includes the soft palate, the base of the tongue, and the tonsils.        Stage II    In stage II nasopharyngeal cancer, the cancer:            - is found in the nasopharynx only or has spread from the nasopharynx to the oropharynx and/or to the nasal cavity. Cancer has spread to one or more lymph nodes on one side of the neck and/or to lymph nodes behind the pharynx. The affected lymph nodes are 6 centimeters or smaller; or      -  is found in the parapharyngeal space. Cancer may have spread to one or more lymph nodes on one side of the neck and/or to lymph nodes behind the pharynx. The affected lymph nodes are 6 centimeters or smaller.            The oropharynx is the middle part of the throat and includes the soft palate, the base of the tongue, and the tonsils. The parapharyngeal space is a fat-filled, triangular area near the pharynx, between the base of the skull and the lower jaw.       Stage III     In stage III nasopharyngeal cancer, the cancer:            - is found in the nasopharynx only or has spread from the nasopharynx to the oropharynx and/or to the nasal cavity. Cancer has spread to one or more lymph nodes on both sides of the neck. The affected lymph nodes are 6 centimeters or smaller; or      - is found in the parapharyngeal space. Cancer has spread to one or more lymph nodes on both sides of the neck. The affected lymph nodes are 6 centimeters or smaller; or      - has spread to nearby bones or sinuses. Cancer may have spread to one or more lymph nodes on one or both sides of the neck and/or to lymph nodes behind the pharynx. The affected lymph nodes are 6 centimeters or smaller.            The oropharynx is the middle part of the throat and includes the soft palate, the base of the tongue, and the tonsils. The parapharyngeal space is a fat-filled, triangular area near the pharynx, between the base of the skull and the lower jaw.       Stage IV     Stage IV nasopharyngeal cancer is divided into stages IVA, IVB, and IVC.            -  Stage IVA: Cancer has spread beyond the nasopharynx and may have spread to the cranial nerves, the hypopharynx (bottom part of the throat), areas in and around the side of the skull or jawbone, and/or the bone around the eye. Cancer may also have spread to one or more lymph nodes on one or both sides of the neck and/or to lymph nodes behind the pharynx. The affected lymph nodes are 6 centimeters or smaller.     -  Stage IVB: Cancer has spread to lymph nodes between the collarbone and the top of the shoulder and/or the affected lymph nodes are larger than 6 centimeters.      -  Stage IVC: Cancer has spread beyond nearby lymph nodes to other parts of the body.