What are the characteristics of a cancer cell that are recognized by the immune system? Knowledge of the potential target structures for the immune cells is a basic prerequisite for the development of personalized cancer immunotherapies. Scientists from the German Cancer Research Center (DKFZ) and the NCT Heidelberg are publishing a highly sensitive method based on mass spectroscopy to identify such tumor-specific “neoepitopes”. The analytical method is designed to detect these low-abundance protein fragments and requires minimal amounts of sample material.