Gastric GIST

R. Brooke Jeffrey, MD

Key Facts

Terminology

Submucosal tumor of GI tract derived from interstitial cells of Cajal

Imaging

Hypo- or hypervascular, well-circumscribed, submucosal mass on arterial phase images; ulceration and necrosis common on CECT
PET superior to CT in predicting early response to Gleevec
Hypermetabolic foci for both primary tumor and metastases
Best diagnostic clue: Well-circumscribed, submucosal mass extending exophytically from GI tract
Best imaging tool: CECT, PET
Nonenhancing necrotic or hemorrhagic areas

Top Differential Diagnoses

Gastric lymphoma
Sarcoma invading stomach
Exophytic gastric carcinoma
Submucosal GI lipoma

Pathology

Distinct, not synonymous with leiomyoma/sarcoma; may not be diagnosed by light microscopy alone

Clinical Issues

Mass effect from bulky tumor; GI bleed when ulcerated; nausea, vomiting, weight loss
Excellent prognosis for completely resected benign lesions
Good response to chemotherapy (Gleevec) in patients with metastatic disease and c-KIT mutation
Prognosis often depends on tumor size
- Poor if > 5 cm

(Left) Anatomic depiction of a gastric stromal tumor shows an exophytic submucosal mass

with internal necrosis. (Right) Axial CECT shows a soft tissue density left upper quadrant mass. The origin of the mass may not be evident, except for a small projection

into the gastric lumen.

(Left) Axial CECT shows an exophytic gastric mass

with a thick enhancing wall and a large central cavitation containing gas, indicating communication with the gastric lumen. Note the extensive central necrosis

of the liver metastasis, typical of GIST. (Right) Axial CECT demonstrates a large lobulated mass arising from the greater curvature of the stomach. The mass is sharply marginated with large foci of necrosis and invades the pancreas, extending to the splenic vein

TERMINOLOGY

Abbreviations

Gastrointestinal stromal tumor (GIST)

Definitions

Submucosal tumor of gastrointestinal (GI) tract derived from interstitial cells of Cajal

IMAGING

General Features

Best diagnostic clue
- Well-circumscribed, submucosal mass extending exophytically from GI tract
Location
- Stomach most common site (2/3 of cases)
- Small bowel (especially duodenum) 2nd most common site
- May occur anywhere in GI tract
- Rarely occurs in esophagus (leiomyoma more common)
Size
- Variable; large mass may be > 5 cm
Morphology
- Bulky, well circumscribed, and lobulated
- Often exophytic, may have cystic element

Fluoroscopic Findings

UGI
- Rounded, exophytic, submucosal gastric mass
- Ulcerations common in larger masses

CT Findings

NECT
- Calcifications in 25% of cases
CECT
- Hypo- or hypervascular, well-circumscribed, submucosal mass on arterial phase images; ulceration and necrosis common on CECT
- Sensitivity (93%), specificity (100%)