An exophytic, well-defined submucosal mass of the stomach or small bowel with heterogeneous enhancement, necrosis and no nodes — size, site and mitotic rate decide risk; response to therapy is judged by attenuation, not only size.
Orient first
- Most arise in the stomach, then small bowel; they grow exophytically and rarely obstruct.
- Lymph node metastases are unusual — enlarged nodes suggest another diagnosis (lymphoma, adenocarcinoma).
- Under tyrosine-kinase inhibitors a responding tumour becomes low in attenuation and cystic and may not shrink (Choi criteria — verify).
Acquire the study
- Portal venous phase with water distension; coronal reformats.
The manoeuvre
- Mass arising from the bowel wall, growing out of it; measure in cm in three planes.
- Heterogeneous enhancement, central necrosis, ulceration with gas or contrast in the centre.
- Nodes: absence supports GIST; liver and peritoneal metastases.
- On treatment: attenuation in HU (a ≥ 15% decrease is a Choi response criterion — verify) as well as size.
What confirms it
- An exophytic enhancing submucosal mass with histology and KIT/DOG1 staining.
What licenses you to exclude it
- Bulky nodes favour lymphoma or adenocarcinoma over GIST.
The classic misread
- Calling a treated GIST progressive because it enlarges with cystic change.