*4.3.2 RET fusions*

RET is a proto-oncogene encoding a transmembrane tyrosine kinase receptor for the glial-derived neurotrophic factor family [110].

RET fusions occur in 0.2% of solid tumors, being very typical in specific tumor types, such as thyroid carcinomas [119]. The effect of RET activation is less clear in CRC, but several studies suggest that it might be associated with worse prognosis, poor treatment response, and reduced OS. Due to rarity of this aberration, clinical trials in CRC are not easy to conduct, with data derived mainly from early trials or case reports [110]. Clinicopathological factors associated with RET fusions include right colon location, older age, RAS and BRAF wild-type status, and MSI-H status [119].
