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Gastrointestinal Imaging

E2775. Looking Beyond the GIST of Gastrointestinal Stromal Tumors: A Review of Associated Tumors

Kuroiwa J1,  Lisanti C1,2,  Smith N1,  Schwope R1,2,  Mansfield L.1,2 1. San Antonio Military Medical Center, Fort Sam Houston, TX; 2. Uniformed Services University of the Health Sciences, Bethesda, MD

Address correspondence to C. Lisanti (lisantic@aol.com)

Background Information: Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract, occurring most frequently within the stomach (50% of cases) and small bowel (25%), and were recently classified as a soft tissue sarcoma by the World Health Organization. C-Kit (CD117) expression is a sensitive immunohistochemical marker, and its discovery has led to the development of better treatment with imatinib mesylate, a tyrosine kinase receptor inhibitor. Five percent of GISTs are associated with neurofibromatosis-1 (NF-1), Carney triad, or Carney-Stratakis syndrome. A recent study showed a 66% increase malignancies that were not GISTs at or after the initial GIST diagnosis. Of GISTs occurring within the stomach and small bowel, 20–25% and 40–45%, respectively, are malignant, and nearly one-half of all GIST cases have metastasis at the time of initial presentation. Metastases commonly affect the liver and peritoneum. After participating in this exhibit, the radiologist will be able to list syndromes related to GISTs, identify tumors that are not syndromic and occur at higher frequency with GISTs, follow a practical initial evaluation with emphasis on metastatic and synchronous tumors, and search for residual, metastatic, and metachronous disease at follow-up evaluation.

Educational Goals/Teaching Points: Once GIST is diagnosed, radiologists must search for synchronous tumors, because a higher incidence tumors that are not syndromic at and after GIST diagnosis. Five percent of GISTs occur with NF-1, Carney triad, or Carney-Stratakis syndrome. The goals of imaging after therapy are to evaluate for treatment response using Choi criteria, evaluate for recurrent, residual, or metastatic disease (metastatic disease will usually involve the liver and peritoneum and other sites are uncommon), and search for metachronous tumors (lesions outside of liver and peritoneum should be highly suspect).

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques: In this exhibit, we will review GIST epidemiology, pathophysiology, and common imaging findings, and define synchronous, metachronous, and metastatic tumors. We will review syndromes involving GIST (5% of GISTS occur in patients with NF-1 syndrome, Carney triad, or Carney-Stratakis syndrome) as well as synchronous and metachronous tumors occur at higher rates in patients with GIST but are not syndromic. We will review the standardized incidence ratio (SIR) for several possible cancers (SIR = 6: ovarian carcinoma; SIR = 4 and < 6: sarcomas, neuroendocrine-carcinoid, small intestine adenocarcinoma, papillary thyroid cancer, and renal cell carcinoma; SIR = 2 and < 4: adenocarcinomas [colorectal, hepatobiliary, gastric, and pancreatic]; SIR > 1 and < 2: non-Hodgkin lymphoma, uterine adenocarcinoma, non–small-cell lung cancer, and urothelial carcinoma of the bladder). C-Kit expression is common with GISTs and their metastases but not common in their related tumors (syndromic and not syndromic).

Conclusion: GISTs are commonly associated with other malignancies in both syndromic and not syndromic fashion. Radiologists should be keenly alert for the possibility of synchronous or metachronous malignancies that are not GIST, especially if the lesion is not within the liver or peritoneum.