Gastrointestinal: A gastrointestinal stromal tumour (GIST) arising in a Meckel's diverticulum

Abstract

A 39-year-old man who had 4 years previously undergone a laparoscopic appendicectomy for acute appendicitis was admitted with sudden onset severe lower abdominal pain. Initial examination revealed focal peritonism in the right iliac fossa, temperature of 39°C and tachycardia (96 bmp). White blood cell count was 16 × 109/l. Contrast enhanced abdominal CT was done 10 hrs after admission. The coronal reformatted image of the CT scan (Figure 1) demonstrated a segment of thickened ileum, inseparable from which was a blind ending loop of small bowel with a mixed attenuating mass within the lumen (arrow). There were no features of small bowel obstruction or free intraperitoneal fluid or air. A diagnosis of an inflamed Meckel's diverticulum or a small bowel tumour was suggested. At laparotomy, a large inflamed Meckel's Diverticulum was seen arising from the antemesenteric border of the ileum (Figure 2a). The diverticulum was resected along with a segment of ileum and a side-to-side ileo-ileal anastomosis was performed. Histological examination with haematoxylin and eosin stain (Figure 2b, magnification ×40) revealed a well-circumscribed lesion in the wall of the small bowel composed of fascicles of bland spindle cells with a central cystic area lined by inflamed small intestinal and pyloric epithelium. Immunohistochemistry confirmed an intermediate risk gastrointestinal stromal tumour (GIST) with positive staining with antibodies to CD34, CD117 and delay of gestation 1 (DOG1) antigen (Figure 2c, magnification ×10), and a Ki-67 proliferation index of 5%. A connection of the central cyst to the bowel lumen was not demonstrable, but in view of the appearance and position of the lesion the features were thought to be consistent with a GIST originating in a Meckel's diverticulum and occluding the neck of the diverticulum. Well differentiated endocrine carcinoma (carcinoid) is the most common tumour in this location and only 11 cases of GIST arising in a Meckel's diverticulum have been reported in the last decade. In the majority of histologically suspected GISTs a combination of CD117 and DOG1 immunostaining is sufficient to confirm the diagnosis. Modes of presentation including gastrointestinal bleeding, perforation, paraneoplastic deep vein thrombosis and incidental finding upon imaging or laparotomy. The patient made an uncomplicated recovery and as the GIST was completely excised and had a low proliferation index, no further therapy was necessary. He remains well two years postoperatively. Contributed by