Molecular diagnostics are revolutionising our understanding and treatment of cancer. Our concept of what are common and what are rare cancers has also been challenged. This all day workshop will discuss new approaches to tumour classification, with a focus on genetic reclassification. We will explore what this means for those diagnosing and treating cancer patients and the program will include an overview of the principles of molecular diagnostics including Next Generation Sequencing (covering the practicalities of testing - which tests for which cancers, what they mean, their limitations, FISH diagnostics, multigene tests in breast cancer and much more) as well as how these may be used in the clinic. This overview will be invaluable for all those who want to know more about this rapidly evolving field.