J O Jansen, D S Gardiner*, A Macdonald
Department of Surgery and *Department of Pathology, Monklands Hospital, Monkscourt Avenue, Airdrie ML6 0JS
Correspondence to: Mr A Macdonald, Monklands Hospital, Monkscourt Avenue, Airdrie ML6 0JS E-mail: Angus.Macdonald@laht.scot.nhs.uk
SMJ 2004 49(4): 160-161
Gastro-intestinal stromal tumours are a rare but wellrecognised cause of small bowel obstruction. We report an unusual case of such a tumour causing intermittent obstruction, not by luminal occlusion, but by kinking of the small bowel, through exerting traction on the antimesenteric border of the terminal ileum.
A 72 year-old female presented as an emergency with colicky abdominal pain, distension, vomiting, and absolute constipation. She had experienced a number of similar episodes over the previous 18 months, which had always resolved spontaneously. There was no history of abdominal surgery and no external herniae on examination.
Plain abdominal x-ray revealed multiple dilated loops of small bowel, and a subsequent gastrograffin enema failed to reveal a proximal colonic abnormality. Ultrasound examination of the abdomen and pelvis confirmed the presence of multiple dilated small bowel loops but no cause was identified. Based on the clinical and radiological findings, a diagnosis of small bowel obstruction of unknown cause was made, and the patient was taken to theatre. At laparotomy, an 85mm firm, lobulated, pedunculated tumour was discovered arising from the antimesenteric border of the terminal ileum, approximately 80cm from the ileocaecal valve.(Fig 1) The tumour was lying in the pelvis, and by exerting traction on the small bowel, had kinked and obstructed the ileum. The ileal lumen was widely patent. The regional lymph nodes were enlarged. The tumour and adjacent mesentery were resected with approximately 60 mm of small bowel on either side. A side-to-side stapled anastomosis was fashioned using the “Barcelona” technique. The patient made an uneventful recovery and was discharged home seven days after surgery.
Macroscopic examination of the specimen revealed a predominantly solid tumour with areas of cystic degeneration and haemorrhage. There was no communication with the lumen. Microscopically, the tumour was cellular, composed of small spindle cells and epithelioid cells. There were areas of myxoid degeneration and necrosis. Mitoses were relatively easily identified. Immunohistochemistry showed positive staining for vimentin and smooth muscle actin, but was negative for desmin, S100, CAM 5.2 and CD 34. The appearances were of a gastrointestinal stromal tumour.
Malignant primary small bowel tumours are uncommon, accounting for around 1-2% of all gastrointestinal malignancies.1,2,3 Gastrointestinal stromal tumours (GIST) represent the largest group of primary non-epithelial neoplasms of the gastrointestinal tract, and encompass a number of types, including schwannomas, lipomas, leiomyomas, leiomyosarcomas, and leiomyoblastomas.4,5 Recent evidence suggests that these tumours arise from the interstitial cells of Cajal located in the muscularis propria.6 Although they show remarkable variability in their differentiation pathways, these lesions are grouped together under the umbrella of stromal tumours because of their similar histological appearances and clinical behaviour.5 GISTs may occur anywhere in the gastrointestinal tract, but are most common in the stomach and small bowel.4 Small bowel gastrointestinal stromal tumours may be completely asymptomatic, especially when benign. Symptomatic growths present with either overt or occult bleeding4,6,8,9,10, abdominal pain4,9,10, obstruction4,8,10, perforation4,8,9 or a mass9,10,11. Although occasionally diagnosed pre-operatively, the diagnosis, as in this case, is usually made at laparotomy.10 The behaviour of GISTs is difficult to predict from the histological appearances, and is based as much on macroscopic (principally size), as well as microscopic features, such as mitotic count.4,10 Approximately threequarters of GISTs are histologically benign.4 Malignant GISTs may recur locally after excision or metastasise, usually by the haematogenous route, and less commonly, by transcoelomic or lymphatic spread.4,9,10 The prognosis of malignant GISTs is in the region of 50-60% five-year survival.4,5,9,10 As one would expect for such rare tumours, there is little information regarding the use of adjuvant therapy.
Obstruction, usually by luminal occlusion secondary to a bulky tumour, is a relatively common presenting symtom of gastro-intestinal stromal tumours4,8,10,12,13, but the mechanism responsible in our patient, kinking of the small bowel due to traction by a large, primarily subserosal tumour, is unusual, and has to our knowledge not been reported previously. Small bowel obstruction in the absence of previous abdominal surgery, and without an obvious cause such as an external hernia, always requires careful investigation and, usually, exploration. Intermittent symptoms can lull the surgeon into a false sense of security and unusual pathology, as in this case, should be considered. Unless significant contraindications exist, early exploration is the safest option.
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