user: What are the stages of Skin Cancer ?

assistant: Key Points
                    - After nonmelanoma skin cancer has been diagnosed, tests are done to find out if cancer cells have spread within the skin 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.    - Staging of nonmelanoma skin cancer depends on whether the tumor has certain "high-risk" features and if the tumor is on the eyelid.    - The following stages are used for nonmelanoma skin cancer that is not on the eyelid:         - Stage 0 (Carcinoma in Situ)     - Stage I Stage I nonmelanoma skin cancer. The tumor is no more than 2 centimeters.     - Stage II Stage II nonmelanoma skin cancer. The tumor is more than 2 centimeters wide.     - Stage III     - Stage IV        - The following stages are used for nonmelanoma skin cancer on the eyelid:         - Stage 0 (Carcinoma in Situ)     - Stage I      - Stage II     - Stage III     - Stage IV        - Treatment is based on the type of nonmelanoma skin cancer or other skin condition diagnosed:         - Basal cell carcinoma     - Squamous cell carcinoma     - Actinic keratosis
                
                
                    After nonmelanoma skin cancer has been diagnosed, tests are done to find out if cancer cells have spread within the skin or to other parts of the body.
                    The process used to find out if cancer has spread within the skin 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 following tests and procedures may be used in the staging process:         -   CT scan (CAT scan): A procedure that makes a series of detailed pictures of areas inside the body, taken from different angles. The pictures are made by a computer linked to an x-ray machine. A dye may be injected into a vein or swallowed to help the organs or tissues show up more clearly. This procedure is also called computed tomography, computerized tomography, or computerized axial tomography.    -   MRI (magnetic resonance imaging): A procedure that uses a magnet, radio waves, and a computer to make a series of detailed pictures of areas inside the body. This procedure is also called nuclear magnetic resonance imaging (NMRI).    -   Lymph node biopsy : For squamous cell carcinoma, the lymph nodes may be removed and checked to see if cancer has spread to them.
                
                
                    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 skin cancer spreads to the lung, the cancer cells in the lung are actually skin cancer cells. The disease is metastatic skin cancer, not lung cancer.
                
                
                    Staging of nonmelanoma skin cancer depends on whether the tumor has certain "high-risk" features and if the tumor is on the eyelid.
                    Staging for nonmelanoma skin cancer that is on the eyelid is different from staging for nonmelanoma skin cancer that affects other parts of the body.     The following are high-risk features for nonmelanoma skin cancer that is not on the eyelid:         - The tumor is thicker than 2 millimeters.    - The tumor is described as Clark level IV (has spread into the lower layer of the dermis) or Clark level V (has spread into the layer of fat below the skin).    - The tumor has grown and spread along nerve pathways.    - The tumor began on an ear or on a lip that has hair on it.    - The tumor has cells that look very different from normal cells under a microscope.
                
                
                    The following stages are used for nonmelanoma skin cancer that is not on the eyelid:
                    Stage 0 (Carcinoma in Situ)     In stage 0, abnormal cells are found in the squamous cell or basal cell layer of the epidermis (topmost layer of the skin). 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. The tumor is not larger than 2 centimeters at its widest point and may have one high-risk feature.       Stage II     In stage II, the tumor is either:            - larger than 2 centimeters at its widest point; or     - any size and has two or more high-risk features.              Stage III    In stage III:            - The tumor has spread to the jaw, eye socket, or side of the skull. Cancer may have spread to one lymph node on the same side of the body as the tumor. The lymph node is not larger than 3 centimeters.              or              - Cancer has spread to one lymph node on the same side of the body as the tumor. The lymph node is not larger than 3 centimeters and one of the following is true:                  - the tumor is not larger than 2 centimeters at its widest point and may have one high-risk feature; or       - the tumor is larger than 2 centimeters at its widest point; or       - the tumor is any size and has two or more high-risk features.                          Stage IV    In stage IV, one of the following is true:            - The tumor is any size and may have spread to the jaw, eye socket, or side of the skull. Cancer has spread to one lymph node on the same side of the body as the tumor and the affected node is larger than 3 centimeters but not larger than 6 centimeters, or cancer has spread to more than one lymph node on one or both sides of the body and the affected nodes are not larger than 6 centimeters; or     - The tumor is any size and may have spread to the jaw, eye socket, skull, spine, or ribs. Cancer has spread to one lymph node that is larger than 6 centimeters; or      - The tumor is any size and has spread to the base of the skull, spine, or ribs. Cancer may have spread to the lymph nodes; or     - Cancer has spread to other parts of the body, such as the lung.
                
                
                    The following stages are used for nonmelanoma skin cancer on the eyelid:
                    Stage 0 (Carcinoma in Situ)    In stage 0, abnormal cells are found in the epidermis (topmost layer of the skin). These abnormal cells may become cancer and spread into nearby normal tissue. Stage 0 is also called carcinoma in situ.       Stage I      Stage I is divided into stages IA, IB, and IC.            -  Stage IA: The tumor is 5 millimeters or smaller and has not spread to the connective tissue of the eyelid or to the edge of the eyelid where the lashes are.      -  Stage IB: The tumor is larger than 5 millimeters but not larger than 10 millimeters or has spread to the connective tissue of the eyelid, or to the edge of the eyelid where the lashes are.     -  Stage IC: The tumor is larger than 10 millimeters but not larger than 20 millimeters or has spread through the full thickness of the eyelid.              Stage II    In stage II, one of the following is true:            - The tumor is larger than 20 millimeters.     - The tumor has spread to nearby parts of the eye or eye socket.     - The tumor has spread to spaces around the nerves in the eyelid.              Stage III     Stage III is divided into stages IIIA, IIIB, and IIIC.            -  Stage IIIA: To remove all of the tumor, the whole eye and part of the optic nerve must be removed. The bone, muscles, fat, and connective tissue around the eye may also be removed.     -  Stage IIIB: The tumor may be anywhere in or near the eye and has spread to nearby lymph nodes.     -  Stage IIIC: The tumor has spread to structures around the eye or in the face, or to the brain, and cannot be removed in surgery.              Stage IV    The tumor has spread to distant parts of the body.
                
                
                    Treatment is based on the type of nonmelanoma skin cancer or other skin condition diagnosed:
                    Basal cell carcinoma      Basal cell carcinoma is the most common type of skin cancer. It usually occurs on areas of the skin that have been in the sun, most often the nose. Often this cancer appears as a raised bump that looks smooth and pearly. Another type looks like a scar and is flat and firm and may be white, yellow, or waxy. Basal cell carcinoma may spread to tissues around the cancer, but it usually does not spread to other parts of the body.       Squamous cell carcinoma      Squamous cell carcinoma occurs on areas of the skin that have been in the sun, such as the ears, lower lip, and the back of the hands. Squamous cell carcinoma may also appear on areas of the skin that have been burned or exposed to chemicals or radiation. Often this cancer appears as a firm red bump. The tumor may feel scaly, bleed, or form a crust. Squamous cell tumors may spread to nearby lymph nodes. Squamous cell carcinoma that has not spread can usually be cured.       Actinic keratosis     Actinic keratosis is a skin condition that is not cancer, but sometimes changes into squamous cell carcinoma. It usually occurs in areas that have been exposed to the sun, such as the face, the back of the hands, and the lower lip. It looks like rough, red, pink, or brown scaly patches on the skin that may be flat or raised, or the lower lip cracks and peels and is not helped by lip balm or petroleum jelly.