Biological and clinical review of stromal tumors in the gastrointestinal tract

Submucosal tumors of the gastrointestinal tract (GI tract) mainly consist o f gastrointestinal mesenchymal tumors (GIMTs) that are distributed in the G I tract from the esophagus through the rectum. GIMTs include myogenic tumor s, neurogenic tumors and gastrointestinal stromal tumors (GISTs). The term "GIST" is now preferentially used for the tumors that express CD34 and KIT. GIMTs are composed of spindle or epithelioid cells, and 20% to 30% show ma lignant behavior, including peritoneal dissemination and hematogenous metas tasis. KIT expression and mutations in the c-kit gene are found only in GIS Ts, but not in myogenic or neurogenic tumors. Mutation in the c-kit gene is associated with aggressive features and poor prognosis, and malignant GIST s frequently have mutations in the c-kit gene. The clinicopathological feat ures of GISTs with or without c-kit mutations are markedly different. There fore, GIMTs may be divided into four major categories based on histochemica l and genetic data: myogenic tumors; neurogenic tumors; GISTs with c-kit mu tation; and GISTs without c-kit mutation. The origin of GISTs is not fully understood. However, phenotypical resemblance to the interstitial cells of Cajal (ICCs) and gain-of-function mutations in the c-kit gene may suggest o rigin from ICCs and/or multipotential mesenchymal cells that differentiate into ICCs.