This is a medical question of type : stages 
 What are the stages of Gestational Trophoblastic Disease ? 
 Key Points
                    - After gestational trophoblastic neoplasia has been diagnosed, tests are done to find out if cancer has spread from where it started 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.    - There is no staging system for hydatidiform moles.    - The following stages are used for GTN:         - Stage I     - Stage II     - Stage III     - Stage IV        - The treatment of gestational trophoblastic neoplasia is based on the type of disease, stage, or risk group.
                
                
                    After gestational trophoblastic neoplasia has been diagnosed, tests are done to find out if cancer has spread from where it started to other parts of the body.
                    The process used to find out the extent or spread of cancer is called staging, The information gathered from the staging process helps determine the stage of disease. For GTN, stage is one of the factors used to plan treatment.   The following tests and procedures may be done to help find out the stage of the disease:          -   Chest x-ray : An x-ray of the organs and bones inside the chest. An x-ray is a type of energy beam that can go through the body onto film, making pictures of areas inside the body.    -   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) with gadolinium : A procedure that uses a magnet, radio waves, and a computer to make a series of detailed pictures of areas inside the body, such as brain and spinal cord. A substance called gadolinium is injected into a vein. The gadolinium collects around the cancer cells so they show up brighter in the picture. This procedure is also called nuclear magnetic resonance imaging (NMRI).    -   Lumbar puncture : A procedure used to collect cerebrospinal fluid (CSF) from the spinal column. This is done by placing a needle between two bones in the spine and into the CSF around the spinal cord and removing a sample of the fluid. The sample of CSF is checked under a microscope for signs that the cancer has spread to the brain and spinal cord. This procedure is also called an LP or spinal tap.
                
                
                    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 choriocarcinoma spreads to the lung, the cancer cells in the lung are actually choriocarcinoma cells. The disease is metastatic choriocarcinoma, not lung cancer.
                
                
                    There is no staging system for hydatidiform moles.
                    Hydatidiform moles (HM) are found in the uterus only and do not spread to other parts of the body.
                
                
                    The following stages are used for GTN:
                    Stage I     In stage I, the tumor is in the uterus only.       Stage II    In stage II, cancer has spread outside of the uterus to the ovary, fallopian tube, vagina, and/or the ligaments that support the uterus.       Stage III     In stage III, cancer has spread to the lung.       Stage IV     In stage IV, cancer has spread to distant parts of the body other than the lungs.
                
                
                    The treatment of gestational trophoblastic neoplasia is based on the type of disease, stage, or risk group.
                    Invasive moles and choriocarcinomas are treated based on risk groups. The stage of the invasive mole or choriocarcinoma is one factor used to determine risk group. Other factors include the following:         - The age of the patient when the diagnosis is made.    - Whether the GTN occurred after a molar pregnancy, miscarriage, or normal pregnancy.    - How soon the tumor was diagnosed after the pregnancy began.    - The level of beta human chorionic gonadotropin (-hCG) in the blood.    - The size of the largest tumor.    - Where the tumor has spread to and the number of tumors in the body.    - How many chemotherapy drugs the tumor has been treated with (for recurrent or resistant tumors).        There are two risk groups for invasive moles and choriocarcinomas: low risk and high risk. Patients with low-risk disease usually receive less aggressive treatment than patients with high-risk disease.    Placental-site trophoblastic tumor (PSTT) and epithelioid trophoblastic tumor (ETT) treatments depend on the stage of disease.