Everything you always wanted to know about GIST (but were afraid to ask) An update on GIST pathology

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract. The discovery of the occurrence of activating KIT mutations and KIT expression in GISTs opened the way to the unequivocal diagnosis of these tumors and to their successful treatment with imatinib, a tyrosin kinase inhibitor. Since then, research progress revealed molecular GIST triggers alternative to KIT, implying heterogeneous analytic approaches and prognostic expectations. Several targeted therapies, variably specific for each GIST trigger, have been developed or are being investigated. Thus, GISTs eventually revealed a family of diseases rather than a single tumor type. All these events had an unprecedented impact on pathology practice, constituting at the same time a heavy burden and an exciting challenge, ultimately putting pathologists in the spotlight as never before. This review will discuss the most recent advances concerning GISTs, highlighting the tasks of pathologists facing these tumors, with an emphasis on traps potentially compromising a correct diagnosis.