Cancer is one of the most common human diseases. It is long known that mutations in key regulator genes are hallmarks of all cancer types. Apart from these classical genetic pathways there is more and more evidence that also epigenetic alterations are crucially involved in tumourigenesis. In this review we discuss and summarise recent findings of mechanisms responsible for cancer formation apart from the classic genetic mutations. Furthermore, we show how epigenetic and genetic mechanisms could depend on each other and contribute together to cancer formation. We focus mainly on post-translational histone modifications since they are one of the major epigenetic mechanisms regulating gene expression and when they are imbalanced this can result in cancer.