Diagnosis: GIST (Gastrointestinal Stromal Tumor)
The most likely diagnosis is GIST (option A), given the characteristic presentation of an exophytic swelling on CT in a patient with epigastric pain and fullness without weight loss. 1
Key Diagnostic Features Supporting GIST
Exophytic Growth Pattern
- GISTs characteristically arise from the muscularis propria of the gastric wall and most commonly manifest as exophytic masses that grow outward from the organ of origin 1
- This exophytic pattern is the dominant radiologic manifestation of GISTs, distinguishing them from intramural or intraluminal masses 1
- The stomach is the most common primary site for GIST (60-70% of cases), followed by small intestine (25-30%) 2, 3
Clinical Presentation Matches GIST Profile
- Abdominal/epigastric pain is the most prevalent symptom in GIST patients 3
- Fullness or abdominal distension is commonly reported with larger GISTs 4
- The absence of weight loss does not exclude GIST—many patients present with localized symptoms without constitutional signs 2
- GISTs can be asymptomatic or present with nonspecific symptoms like pain and fullness 2
Why Other Options Are Less Likely
Leiomyoma (Option C)
- Leiomyomas are now understood to be rare in the GI tract since the recognition of GISTs as a distinct entity 1
- GISTs were historically misclassified as leiomyomas before CD117 (KIT) immunohistochemistry became available to distinguish them 1
- True leiomyomas lack CD117 expression, which is present in >95% of GISTs 5, 2
Leiomyosarcoma (Option B)
- Leiomyosarcomas are also now recognized as distinct from GISTs and are much rarer 1
- The clinical presentation and exophytic pattern on CT are more consistent with GIST than leiomyosarcoma 1
Lymphoma (Option D)
- Gastric lymphoma typically presents with diffuse wall thickening rather than an exophytic mass 6
- Lymphoma more commonly causes constitutional symptoms including weight loss, which is absent in this case 6
- The imaging pattern described (exophytic swelling) is atypical for lymphoma
Diagnostic Confirmation Required
Imaging Characteristics to Assess
- GISTs characteristically show hemorrhage, necrosis, or cyst formation appearing as focal areas of low attenuation on CT 1
- Large GISTs (>5 cm) often demonstrate heterogeneous enhancement with cystic or necrotic components 1, 4
Definitive Diagnosis
- Endoscopy with endoscopic ultrasound and cross-sectional imaging (CT/MRI) constitute the diagnostic workup 2
- Histopathological confirmation with CD117 (KIT) immunohistochemistry is essential—approximately 95% of GISTs are CD117-positive 5, 2
- Mutational analysis (c-KIT or PDGFRA genes) should be performed when planning treatment, as 80-90% carry these mutations 5
Clinical Pitfall to Avoid
Do not dismiss GIST based on absence of weight loss or bleeding—while GI bleeding is a common presentation, many patients present with nonspecific abdominal pain and fullness alone, particularly with exophytic tumors that grow outward rather than into the lumen 2, 3, 4