Leendert Looijenga studied biology at the University of Groningen and graduated (cum laude) with a specialization in medical cell biology (1989). After being a visiting scientist (Anthropogenetics, Leiden University), he started the Laboratory for Experimental Patho-Oncology at the Daniel den Hoed Cancer Center (Rotterdam). In 1994, he defended his thesis, "Pathobiology of germ cell tumors of the adult testis: views and news" (Erasmus University Rotterdam), and became initiating scientist and staff member. In 1998, the laboratory moved to the Josephine Nefkens Institute, Department of Pathology. In 2005 he became Professor of Translational Patho-Oncology at the Erasmus MC. Looijenga is leading an active group of clinicians and scientists (in training), related to understanding the processes involved in normal and aberrant gonadal development. This has significant impact on prediction of the individual risk to develop a (malignant) germ cell tumor in time as well as potential for (future) fertility. Identification and application of clinically relevant diagnostic, prognostic and predictive markers is one of the targets. These are applied both on tissues as well as liquid biopsies (serum/plasma/semen). The targets focused on are development of tools for early diagnosis as well as prediction of clinical behavior of the tumor, including systemic treatment sensitivity.