Microscopy: The sections show a well-circumscribed lesion arising from the duodenal wall with continuity with muscularis mucosae and muscularis propria. The lesion is composed of elongated spindled cells arranged in fascicles, embedded within fibrous stroma. The spindle cells show moderate amount of eosinophilic cytoplasm, mild nuclear pleomorphism, vesicular chromatin and small nucleoli. Ectatic vessels are present within the lesion, some of which show calcification of the vascular wall. There are foci of haemorrhage and necrosis. Two mitotic figures are seen in 5 sq mm. The lesion is clear of serosa and longitudinal resection margins. The spindle cells are positive for CD117, negative for desmin, AE1/3, CD31 and S100. Ki67 shows proliferative index of < 1%.
Macroscopy: Labelled "Duodenal GIST flexure". Fragment of Small bowel 47 x 35 mm. 4 mm from the black inked margin there is a polypoid lesion with an outpouching and pushing front onto the serosal surface. Lesion appears cream/brown with areas of haemorrhage measuring in aggregate 50 x 40 x 32 mm. Lesion is 25 mm from the green inked resection margin. Remainder of mucosa appears pale tan.
Conclusion: Duodenal flexure lesion: Gastrointestinal stromal tumour, 50 mm in size, clear of margins. Prognostic Group 2. pT2.