Presentation
Pain while sitting and constipation for 2 years.
Patient Data
The lower rectum shows a T1W isointense, T2W intermediate intensity exophytic pre-sacral mass arising from the posterior wall with diffusion restriction and heterogeneous post-contrast enhancement. The mass is causing a narrowing of the lumen with no significant proximal bowel dilatation. It abuts the internal sphincter and levator ani muscle with no evidence of invasion.
Histopathology and immunohistochemistry favor the diagnosis of gastrointestinal stromal tumor(GIST).
DNA sequence analysis shows KIT mutation.
Case Discussion
Gastrointestinal stromal tumor (GIST) is the most common mesenchymal neoplasm of the gastrointestinal tract, commonly arises from the stomach, followed by the small bowel. Rectum involvement is rare and may be intraluminal or extraluminal.
On MRI, the solid component of the tumor can be hypointense to isointense to adjacent skeletal muscle on T1-weighted images and hyperintense on T2-weighted images. Intratumoral high-intensity may be seen on T1WI, representing hemorrhage. Necrosis can be seen as a high signal intensity on T2W 1.
These tumors tend to have smooth margins without a true capsule and usually don’t present with bowel obstruction or abdominal adenopathy 2.
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