PIK3CA mutations occur at relatively low frequency in most paediatric sarcomas; however, the PI3K/AKT/mTOR pathway is frequently dysregulated in many paediatric sarcoma types through other mechanisms such as excessive activity of upstream receptor kinases and loss of the negative regulator PTEN, which is silenced in 38% of sarcomas [107]. The gene discussed is MTOR; the disease is sarcoma.