High-grade Gastrointestinal Stromal Tumor (GIST)

Jonathan Levi Streeter, MD - Case Coordinator
Aaron David Sodickson, MD, PhD - Radiology Discuss
Miguel N Rivera, MD - Pathology Discussion
Pablo R Ros, MD, MPH - Attending Radiologist

November 25, 2002

Presentation

Imaging Findings

Axial abdominal CT images (no contrast) demonstrate a round, heterogeneous mass (approximately 5-7 cm) on the right side of the abdomen. A small ulceration is visible. No adenopathy is apparent, and contrast material is flowing through the ascending colon. The mass seems to arise from the small bowel, perhaps the ileum.

Differential Diagnosis

Diagnosis

Discussion

The gross images show a mass in association with loops of small bowel. A small ulceration is noted in the mucosa. The cross section reveals a striking amount of hemorrhage. In addition, the tumor mass is friable due to extensive necrosis. On histology, the tumor comes very close to the mucosa of the small intestine. At high power, both spindle and epithelial-type cells are visible. The C-kit stain (CD117), diagnostic for GIST, is positive in the tumor cells. This tumor is considered high grade because of the large number of mitoses.

Radiology Discussion

Gastrointestinal stromal tumor (GIST) is a mesenchymal spindle cell (70-80%) or epithelioid (20-30%) neoplasm. The diagnosis is based on a positive C-kit (CD117) stain, which is a tyrosine kinase growth factor receptor. Some of these tumors also respond dramatically to STI571 (Gleevec). "GIST" is relatively new terminology; these would once have been called leiomyomas, leiomyoblastomas, and/or leiomyosarcomas.

GISTs occur most often in the stomach (60-70%), followed by the small bowel (20-30%; ileum > jejunum > duodenum), the colon/rectum (5%), and the esophagus (5%). The majority are benign; 10-30% are malignant. The differentiation is made according to the number of mitoses counted during histological examination. Several factors increase the likelihood of malignancy in GIST. These include extragastric location, size greater than 5 cm, central necrosis, extension into adjacent organs, and metastases (occurring in the liver and peritoneum much more frequently than in the lung, bone, or lymph nodes).

GISTs can exhibit one of two growth patterns. In the endoenteric growth pattern, tumors tend to be submucosal or intramural; these are more likely to ulcerate early on, and bleeding typically leads to early diagnosis. An exoenteric pattern is much slower, and the tumor is typically not found until a palpable mass (or bleeding from excavation into bowel lumen) is noted. Among gastric GIST, 50% are intramural, 35% are exogastric, and 15% endogastric. Among small bowel GIST, 65% are predominantly exoenteric, 15% are intramural, 10% are intraluminal, and 5% are pedunculated (intraluminal). Frequent ulceration from the stretching of the mucosa over the mass can lead to a "bull’s-eye" appearance on upper GI or small bowel follow-through. In some cases, an ulcer or fistula may be continuous with central necrosis.

The differential diagnosis of cavitary small bowel lesions includes lymphoma, GIST, primary adenocarcinoma, and metastasis (especially melanoma).

References

Dähnert, Wolfgang. Radiology Review Manual, 4th ed., Lipincott Williams & Wilkins 1999.

Levy, Angela. Gastric and Duodenal Malignant Neoplasms: Radiologic-Pathologic Correlation, AFIP notes 2002.

Thompson, William. Focal Small Bowel Disease, AFIP notes 2002.

• Return to the Teaching Case Database search page
• Return to Professional Education
  
• About BrighamRAD

Dear Visitors: Nothing on this World Wide Web site should be considered medical advice. Only your own doctor can help you make decisions about your medical care. It is not the policy of the Brigham and Women's Hospital Department of Radiology to provide consultation on the World Wide Web or via e-mail. If you have a specific medical question or are seeking medical care, please call the Brigham and Women's Hospital toll-free physician referral line at 1-800-294-9999.

Is this a mirrored page?
The official homepage of the BrighamRAD Teaching Case Database is http://brighamrad.harvard.edu/education/online/tcd/tcd.html