A 49-year-old male with neoformation of 3 cm to 1 cm from the anal margin.
Biopsy was compatible with GIST (CD-117: +/DOG1: +).
Magnetic resonance imaging (MRI) revealed a tumor in the right anterolateral wall of the rectum.
18F-FDG PET/CT described focal lesion accumulation with a standardized uptake value (SUV) of up to 9.
Neoadjuvant treatment with imatinib 400 mg/day was started.
Three months later, an 18F-FDG PET/CT was performed and no pathological accumulation was observed.
A transanal resection was performed.
The pathology described tumor cells with positivity for CD-117 and DOG-1 and viable tumor (< 5%) with free margins of involvement.
The patient is 18 months later free of disease.
