Gastrointestinal stromal tumors: a comprehensive radiological review

Abstract

Gastrointestinal stromal tumors (GISTs) originating from the interstitial cells of Cajal in the muscularis propria are the most common mesenchymal tumor of the gastrointestinal tract. Multiple modalities, including computed tomography (CT), magnetic resonance imaging (MRI), fluorodeoxyglucose positron emission tomography, ultrasonography, digital subtraction angiography, and endoscopy, have been performed to evaluate GISTs. CT is most frequently used for diagnosis, staging, surveillance, and response monitoring during molecularly targeted therapy in clinical practice. The diagnosis of GISTs is sometimes challenging because of the diverse imaging findings, such as anatomical location (esophagus, stomach, duodenum, small bowel, colorectum, appendix, and peritoneum), growth pattern, and enhancement pattern as well as the presence of necrosis, calcification, ulceration, early venous return, and metastasis. Imaging findings of GISTs treated with antineoplastic agents are quite different from those of other neoplasms (e.g. adenocarcinomas) because only subtle changes in size are seen even in responsive lesions. Furthermore, the recurrence pattern of GISTs is different from that of other neoplasms. This review discusses the advantages and disadvantages of each imaging modality, describes imaging findings obtained before and after treatment, presents a few cases of complicated GISTs, and discusses recent investigations performed using CT and MRI to predict histological risk grade, gene mutations, and patient outcomes.

Keywords: Acute abdomen; Gastrointestinal stromal tumors; Magnetic resonance imaging; Multidetector computed tomography; Proto-oncogene proteins c-kit.

Fig. 1

Low-risk gastrointestinal stromal tumor (epithelioid cell type). A 49-year-old male with a gastrointestinal stromal tumor arising from the stomach. An oval exophytic tumor arising from the stomach showing a slightly low density on noncontrast CT (a: arrow) and homogenous enhancement shown in the venous phase (b: arrow). Hematoxylin–eosin stain showing spindle cell-type tumors (c) but no mitosis in the high-power field (d)

Fig. 2

High-risk gastrointestinal stromal tumor (spindle cell type). A 65-year-old male with a gastrointestinal stromal tumor arising from the stomach. A lobulated tumor that originated from the stomach with exophytic growth includes a solid component (a and b: arrows) and cysts with thickened walls (a and b: arrowheads). The solid component shows moderate enhancement in the arterial phase continuing the gastric wall, and the cystic portion dislocates the spleen on multiplane CT images. Hematoxylin–eosin stain showing epithelioid-type tumor cells (c) and multiple mitoses in the high-power field (d: arrows)

Fig. 3

Enhancement of a small gastrointestinal stromal tumor in the small bowel. A 70-year-old male with a small gastrointestinal stromal tumor in the small bowel. An endophytic round mass is observed (a–c: arrows). The mass shows marked enhancement in the arterial (b: arrow) and venous phases (c: arrow) and washout patterns

Fig. 4

Enhancement of a small gastrointestinal stromal tumor in the stomach. A 49-year-old male with a small gastrointestinal stromal tumor in the stomach. An intramural round circumscribed mass is seen in the anterior gastric wall (a–c: arrows). The mass shows mild enhancement in the arterial phase (b: arrow) and enhancement equivalent to that of the gastric wall in the venous phase (c: arrow)

Fig. 5

Early venous return. A 46-year-old male with an exophytic gastrointestinal stromal tumor of the small bowel. The tumor contains enlarged vasculature in both the central and peripheral areas (a, b: arrows). Although the ileocecal vein is not enhanced (b: black arrowhead), a dilated vein shows contrast enhancement suggesting early venous return from the small bowel mass in the arterial phase (b: white arrowhead)

Fig. 6

Cystic degeneration of a gastrointestinal stromal tumor in the stomach. A 66-year-old male with a submucosal tumor in the stomach detected via upper gastrointestinal endoscopy. Contrast-enhanced CT showing an endophytic tumor (a: arrow) and fluid collection (a: asterisk). A tumor consisting of a red solid component with a cavity at the center on a surgical specimen (b)

Fig. 7

Calcification in a gastrointestinal stromal tumor in the stomach. A 52-year-old male with a cystic mass in his left-upper abdomen detected via ultrasonography during an annual health check-up. Contrast-enhanced CT showing a solid tumor arising from the gastric wall associated with cystic degeneration. Calcification in the solid component can be seen (a: arrow). Bone tissue in the solid component is shown in a surgical specimen (hematoxylin–eosin stain: × 100) (b: asterisk)

Fig. 8

Hepatic metastasis of a gastrointestinal stromal tumor in the small bowel. A 69-yar-old female with a gastrointestinal stromal tumor in the small bowel and hepatic metastasis. A slightly hyperenhanced mass is seen in the liver in the arterial phase (a: arrow) and shows washout in the portal venous phase (b: arrow). Bulky masses in the small bowel are seen (a and b: arrowheads)

Fig. 9

Peritoneal metastasis of a gastrointestinal stromal tumor in the small bowel. A 67-year-old female with a gastrointestinal stromal tumor in the small bowel presenting with peritoneal sarcomatosis. On noncontrast CT, the primary lesion is seen as a high-attenuation area, indicating intratumoral hemorrhage (a: asterisk). Contrast-enhanced CT showing multiple round masses in the greater omentum adjacent to the bowels, suggesting serosal implants (b: arrows)

Fig. 10

Imaging findings after imatinib therapy. A 54-year-old male with high-risk gastrointestinal stromal tumor in the small bowel was treated with imatinib. A bulky tumor with degeneration (a: arrows) and hepatic metastases (b: arrowheads) are seen in the venous phase of contrast-enhanced CT. The primary small bowel lesion decreased in size (c: arrow). Hepatic metastases show no change in size, whereas the contrast enhancement markedly decreased (d: arrowheads)

Fig. 11

Multiple gastrointestinal stromal tumors associated with neurofibromatosis type 1. A 70-year-old male presented with melena. His hemoglobin level decreased from 14.0 g/dL to 6.0 g/dL within 1 month. He was diagnosed with neurofibromatosis type 1. Axial contrast-enhanced CT images showing multiple hypervascular tumors of various sizes in the small bowel (a, b: arrows). Note that multiple skin lesions are compatible with neurofibromas (a, b: arrowheads). Laparotomy reveals multiple exophytic nodules in the small intestine (c)

Fig. 12

Multiple gastrointestinal stromal tumors associated with a familial gastrointestinal stromal tumor. A 78-year-old male presented with anemia. Coronal and axial contrast-enhanced CT in the venous phase demonstrate a homogeneous hypovascular tumor in the stomach (a: arrow) and multiple homogeneous or heterogeneous hypervascular tumors in the duodenum and jejunum (a and b: arrowheads). Diverse imaging findings (i.e., hypovascular vs. hypervascular and homogeneous vs. heterogeneous) are observed even in the same patient

Fig. 13

Gastrointestinal bleeding caused by a gastrointestinal stromal tumor in the small bowel. A 59-year-old female visited an emergency department with a continuous tarry stool after hematochezia. Her hemoglobin level decreased from 12.0 g/dL to 8.3 g/dl for a day. Contrast-enhanced CT showing a hypervascular tumor in the small intestine (a: arrow). The enlarged vein continuing to the tumor is markedly enhanced in the arterial phase (a: arrowhead). Double balloon endoscopy showing a submucosal tumor with ulcer (b). Inoue A. Gastrointestinal stromal tumor (GIST). (In Mizunuma K, et al., eds. Diagnosis Imaging and Intervention Therapy of Abdominal Emergencies. Tokyo: MedicalView; 2018. P200, Fig. 1

Fig. 14

Ruptured gastrointestinal stromal tumor in the small bowel. A 72-year-old male presented with epigastralgia and his pain gradually migrated from the upper abdomen to the right lower abdomen, resembling a symptom of acute appendicitis. Axial (a) and coronal (b) images of contrast-enhanced CT in the arterial phase showing the hypervascular tumor (arrows) in the small bowel and adjacent fluid collection (asterisks) with fistula (arrowheads). Laparotomy showing that the tumor ruptured into the mesentery (c)

Fig. 15

Mesenteric volvulus caused by an exophytic gastrointestinal stromal tumor in the small intestine. A 74-year-old male presented with abdominal discomfort and bloating. Contrast-enhanced CT shows the whirl sign in the mesentery, but enhancement is preserved in the involved mesenteric vessels (a: arrows). A > 10 cm tumor is seen in the pelvis (b: asterisk). The dilated drainage vein with enhancement is observed adjacent to the tumor (b: arrowhead). Laparotomy showing a large exophytic lobulated tumor arising from the small bowel on the antimesenteric side