A 60-year-old man presented with abdominal pain and melena for 3 months. Upper gastrointestinal endoscopy results suggested jejunal diverticula with normal mucosa. Histologic workup revealed a gastrointestinal stromal tumor (GIST) (spindle cell type, >5 mitoses per 5 mm2, CD117 positive, DOG1 positive, Ki-67 index: 5%–7%). Abdominal CT revealed well-defined, heterogeneously enhancing circumferential wall thickening with an exophytic component involving the distal jejunum. Multiple omental deposits, mesenteric deposits, and hepatic lesions were also noted. Fine-needle aspiration cytology results suggested metastatic GISTs. The patient had no bone pain or skeletal-related event and was given a tyrosine kinase inhibitor (imatinib), the mainstay of treatment. Fluorodeoxyglucose PET/CT (Figs 1, 2) performed 2 months later revealed extensive metastasis to lymph nodes and bones.
Figure 1:
Fluorodeoxyglucose PET/CT images in a 60-year-old man 2 months after treatment with imatinib for gastrointestinal stromal tumor. (A) Maximum intensity projection image shows multiple foci of abnormal tracer uptake in the body. (B, C) Transaxial fused PET/CT images show supraclavicular, mediastinal, and axillary lymphadenopathy and sternal bone lesions (arrows).
Figure 2:
(A) Transaxial CT and (B) fused PET/CT images in the same patient show a metabolically inactive hypoattenuating lesion (arrows) in the right liver lobe. (C) Transaxial pelvic CT and (D) fused PET/CT images show multiple metabolically active bone lytic lesions (arrows).
GISTs represent 1% of malignant tumors of the digestive tract. They are derived from the interstitial cells of Cajal, which serve as a gut pacemaker by creating the basal electrical rhythm leading to peristalsis (1). The most common site of GIST is the stomach (60%–70%), followed by the small intestine (20%–30%) and colorectum (5%–10%). They rarely arise from the mesentery, omentum, and retroperitoneum (2). GIST metastasizes commonly to the liver and peritoneum (3) and rarely to other visceral organs, lungs, pleura, bones, or brain (4). Metastatic involvement of the lymph nodes (1%–2%) and bone (0.47%) are highly uncommon (5).
Footnotes
Authors declared no funding for this work.
Disclosures of conflicts of interest: V.K.S. No relevant relationships. K.M. No relevant relationships. M.O. No relevant relationships.
Keywords: Gastrointestinal Stromal Tumors, GIST, Metastatic GIST, Imatinib, FDG PET/CT, Abdomen/GI
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