Several diagnostic tests are used to determine the stage of cancer, including: - Imaging Tests: CT scans, MRI, PET scans, and X-rays help visualize the size and spread of the tumor. - Biopsies: Tissue samples are examined under a microscope to assess the type and extent of cancer. - Blood Tests: Certain types of cancer release substances that can be detected in the blood. - Endoscopy: A procedure to look inside the body using a flexible tube with a light and camera.