Image of the Month—Diagnosis

The pathologic finding was a spindle-celled mesenchymal neoplasm (CD 117⁺; mitotic index, 2 per 50 high-power fields) with erosion of the mucosa of the small bowel, at most 6.5 cm in diameter. Given all of the immunohistopathologic results, we classified the tumor as a GI stromal tumor (GIST) of the small bowel.

With an incidence of 1.5 to 2 cases per 100 000 people, the GIST is considered to be a rare disease that can appear anywhere in the GI tract.^1,2As is also shown in the literature, our case reflects the difficulties for diagnosis and management of these tumors owing to a wide range of nonspecific symptoms depending on the location of the disease and its complications.^2,3Studies have reported GI bleeding as one of the main symptoms of GISTs, appearing in up to 50% of all cases.^3-5

The origin of only 15% of all bleeding concerning the digestive tract is in the lower distal part of the musculus suspensorius duodeni.⁶Bleedings of the small bowel are rare and make up approximately 1% of these lower GI bleedings. In most cases, the blood comes from a vascular lesion or angiodysplasia of the small intestine. It is rarely caused by an ischemic or inflammatory process or even a bleeding Meckel diverticulum. Although GISTs comprise less than 1% of all tumors of the digestive tract, they are responsible for 5% to 10% of GI hemorrhages that originate in small-bowel tumors.⁷

Principally, GISTs can arise throughout the GI tract, as these mesenchymal tumors originate from the interstitial Cajal cells, so-called pacemaker cells.^1,4,5The neoplastic development of GISTs is caused by a mutation of the expressed tyrosine kinase c-kit (CD117) activity receptor.

Retrospective studies have shown that GISTs are most often localized in the stomach (up to 70%) and the small bowel (20%-30%) than in other parts of the GI tract.^5,8,9The authors of a long-term study from Taiwan, published in 2006, reported that 100 GISTs of the small bowel, of which 63% were localized in the jejunum, were mostly found in the proximal jejunum, with a medium distance of 30 cm to the musculus suspensorius duodeni.¹⁰As confirmed by numerous retrospective studies, the most common symptom of GISTs located in the small bowel is GI bleeding, followed by nonspecific abdominal pain. Symptoms of intestinal occlusion or peritonitis because of tumor perforation into the peritoneal cavity are rare.^1,4,5,10,11Approximately 10% to 30% of all GISTs are discovered incidentally during endoscopy, laparoscopy, as well as computed tomography while patients are asymptomatic.⁸

There is still no evidence for which sex predominantly develops GISTs. According to most published studies, these tumors often occur in middle age, with a peak in the fifth and sixth decades of life.^1,4,5,9-11Tumor size and mitotic rate are the most important criteria for predicting tumor behavior.^4,9-11

Findings of previously published studies led to a malignancy risk classification of GISTs: very low, low, intermediate, and high risk. Our patient's tumor was classified as having an intermediate risk of malignant progress.

Complete surgical en bloc extirpation remains the standard therapy for all nonmetastatic GISTs.^1,8As there is no evidence of GISTs metastasizing into the regional lymph nodes, a lymphadenectomy is not routinely performed.^3,9,10The most common localizations of GIST metastases are the liver and the peritoneal cavity. The lungs and/or bones are sometimes affected.¹⁰For any metastatic disease, adjuvant treatment with imatinib mesylate seems to be effective and is recommended. Apart from the question of long-term benefit, optimal dosing, and duration of drug therapy, which have not yet been determined, the effect of neoadjuvant treatment has to be observed in ongoing prospective randomized trials.^1,8

Gastrointestinal stromal tumors of the small bowel are rare but can cause life-threatening GI bleeding, which is very difficult to diagnose. Segmental resection of the small bowel is the gold standard in cases of preoperatively diagnosed GISTs as well as in emergency situations when explorative laparotomy has to be performed to localize and stop the GI bleeding. There are numerous ongoing clinical trials, the results of which will give us a base to establish a risk-adapted concept to link the surgical treatment with the application of imatinib mesylate and similar drugs.

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Correspondence:Jürg Metzger, MD, Department of Visceral Surgery, Cantonal Hospital Lucerne, 6000 Lucerne, Switzerland (juerg.metzger@ksl.ch).

Accepted for Publication:September 24, 2008.

Author Contributions:Study concept and design: Fischer and Metzger. Acquisition of data: Fischer, Nagel, and Metzger. Analysis and interpretation of data: Fischer. Drafting of the manuscript: Fischer. Critical revision of the manuscript for important intellectual content: Nagel, Fischer, and Metzger. Administrative, technical, and material support: Nagel and Metzger.

Financial Disclosure:None reported.