[Imaging of gastrointestinal stromal tumors]. / Imagerie des tumeurs stromales digestives.

Gastrointestinal stromal tumors (GIST) arising from interstitial cells of Cajal, represent the first type of solid tumor, which is very sensitive to a specific molecularly targeted tyrosine kinase receptor blocker (i. e., imatinib). On CT, which is considered as the reference technique, GISTs typically present as large, well-delineated, heterogeneous and sometimes exophytic masses. In contrast with the absence of lymph node involvement, hepatic metastasis as well as mesenteric involvement can be observed. MR-enteroclysis is indicated to investigate the local extent of the disease in specific cases whereas MR imaging is used to detect hepatic metastasis. Because of a specific treatment, contrast-enhanced imaging is needed for the follow-up of treated tumors. Evaluation of tumor response to treatment is best assessed with CT which still remains the reference imaging technique whereas FDG-PET imaging is used in specific cases.

[Gastrointestinal stromal tumors: role of computed tomography before and after treatment]. / Tumeurs stromales digestives: rôle de la tomodensitometrie avant et apres traitement.

Gastrointestinal stromal tumors (GIST) are the most frequent mesenchymal tumors of the gastrointestinal tract. They are generally located in the stomach or the small bowel and the potential for becoming malignant varies. Due to their expression of c-kit protein, a positive diagnosis as well as a specific targeted treatment by molecular biology (imatinib) are available. Computed tomography is the best imaging method for diagnosis, staging and follow-up of GIST. They appear as a well-defined exophytic mass with heterogeneous enhancement after intravenous injection of iodinated contrast material. They may contain areas of necrosis and/or haemorrhage and enlarged lymph nodes are exceedingly rare. Most common metastatic sites are the liver and mesentery. Large tumour size and liver or mesenteric metastases are computed tomography criteria for a high malignant potential. After treatment, decrease in tumour size, number and density of lesions and the disappearance of enhancing nodules suggest a positive response to imatinib therapy, whereas a new enhancing nodule within a mass is the usual pattern of recurrence. Positron emission tomography may be useful in specific cases when clinical data are inconsistent with computed tomography criteria.