Gastrointestinal stromal tumor (GIST) - huge
Urinary frequency and abdominal distension.
CT abdomen / pelvis
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The majority of the abdominal cavity is taken up by a very large mass which has both solid and cystic / necrotic areas. No calcification. No convincing site of origin can be identified, due to the enormous size, however it appears to be centered on the small bowel mesentery, given the displacement of small bowel anteriorly, and location anterior but separate from the pancreas.
The patient went on to have a laparotomy and resection of the mass, complicated by intra-operative rupture.
MACROSCOPIC DESCRIPTION: Small bowel, 30mm long. Within the anti-mesenteric wall of the jejunum is an rubbery mixed solid/cystic cream mass, 240x170x170mm, 130x130mm. There is a large central empty cavity within the tumour containing extensive quantities of tan necrotic debris. The peripheral tumour mixed solid/cystic tan tissue from 5-25mm thick. There is a full thickness rupture (150mm long) rupture through a thin part of the tumour into the central cavity (edges inked green). The muscularis propria is markedly attenuated but no definite invasion is seen and the serosa away from the perforation appears intact and smooth (inked blue). The tumour is 10mm from the bowel margins and 20mm from the mesenteric margin.
MICROSCOPIC DESCRIPTION: Sections show a tumour within the wall of the jejunum composed of short fascicles of plump, relatively monomorphic spindle cells. Tumour cells have oval nuclei with fine vesicular chromatin. Nucleoli are focally prominent. Cytoplasmicic vacuoles are prominent. Mitotic figures are present up to 9 per 50 hpf. Small thin walled vessels are prominent within the tumour stroma and there is a light infiltrate of lymphocytes, eosinophils and plasma cells. Cystic foci noted macroscopically show necrosis, haemorrhage and fibrinoid debris but lack an epithelial cell lining. The tumour invades through the muscularis propria into the subserosa. Lymphovascular and perineural invasion are not seen. The bowel margins are free of tumour. No tumour is seen in four lymph nodes.
By immunohistochemistry tumour cells are cKIT+ (paranuclear), DOG1+, S100 equivocal (patchy weak nuclear staining), CD34-, desmin- and SMA+ (weak).
DIAGNOSIS: Gastrointestinal stromal tumour (GIST) with high malignant potential.
This case illustrates an unusually large, necrotic GIST.
Case courtesy of Dr Janette Vincent, Royal Melbourne Hospital, Australia