Bioinformatics is essential in clinical oncology and research. Combining biology, computer science and mathematics, bioinformatics aims to derive useful information from clinical and biological data, often poorly structured, at a large scale. Bioinformatics approaches have reclassified certain cancers based on their molecular and biological presentation, improving treatment selection. Many molecular signatures have been developed and, after validation, some are now usable in clinical practice. Other applications could facilitate daily practice, reduce the risk of error and increase the precision of medical decision-making. Bioinformatics must evolve in accordance with ethical considerations and requires multidisciplinary collaboration. Its application depends on a sound technical foundation that meets strict quality requirements.