His research is focused on development and application of diagnostic, prognostic and predictive markers (focussing on Barret esophagus, head and neck- and gonadal development including germ cell cancers as well as (in)fertility). The latter topic relates to regulation of Disorders of Sex Development (DSD), pluripotency and cisplatin sensitivity and resistance, sex determination (gonadal development), germ cell maturation and transformation. Various approaches are applied, including integrated omics. During the last 25 years, a large series of human germ cell tumors, over 2000 individual cases, freshly frozen, including control tissue (peripheral blood, serum, etc.) as well as clinical follow up, has been collected. The archive has proven itself to be highly informative for both fundamental as well as translational research.