Many types of cancer have been proven to be presumptively service-connected due to the military’s history of using certain types of chemicals such as Agent Orange or contaminated water at bases such as Camp Lejeune. If you served in a designated location such as Vietnam during the time periods VA recognizes for presumptive exposure, and you have a cancer diagnosis that VA recognizes is presumptively service-connected for that exposure, VA will establish service connection on a presumptive basis, and you will not need to take additional steps to prove the nexus to service.