By using multi-detector row CT becomes more practical and useful in the detection and evaluation of gastric malignancies and the variety of benign conditions that affect the stomach2. Thus, the purpose of this study was to describe the CT features of gastric malignancies.
The author retrospectively reviewed the CT images and radiological records of 89 patients having a definite pathological diagnosis of adenocarcinoma, malignant lymphoma and malignant GIST of the stomach. The patients were seen at Khon Kaen Hospital between March 2014 and February 2017. The study was approved by the Institutional Review Board of Khon Kaen Hospital, Khon Kaen, Thailand.
The study population who received a definite pathologic diagnosis of gastric adenocarcinoma was 78 patients (87.64%), malignant gastric lymphoma was 4 patients (4.49%) and malignant gastric GIST was 7 patients (7.87%). All 89 patients of gastric malignancy included 46 men (51.69%) and 43 women (48.31%). The age range of the study population was 28-85 years and the mean age was 60 years. In this study excluded any patients having a definite pathological diagnosis of adenocareinoma, malignant lymphoma and malignant GIST of stomach who had received any previous treatment by surgery and/or chemotherapy.
An optimum CT technique requires high spatial resolution, proper gastric distention, and proper timing of contrast media injection in order to detect subtle changes in the gastric wall and to accurately stage tumors3.
For dedicated imaging of the stomach, adequate distention is essential. If the entire stomach is not well distended, the disease may be overlooked or, conversely, the collapsed gastric wall may mimic disease. Recently, there has been interest in using alternative oral contrast agents for CT of the gastrointestinal tract. We prefer to use water as an oral contrast agent in patients with suspected gastric disease because it is inexpensive (usually free), well-tolerated, distends the stomach well, allows good visualization of the enhancing wall, and dose not interfere with the manipulation of the 3D data sets. When CT was performed specifically to evaluate the stomach, the patients were given about 500-1000 ml of water approximately 15 minutes before scanning4.
Gastric imaging has been improved by the introduction of multi-detector row CT scanners. We currently used a 16-detector row CT scanner with a 0.75-second tube rotation (Activion 16 ; Toshiba) in all 89 patients of this study. The scan included the whole abdomen from the diaphragm to the iliac crest with 1 mm. section collimation, at a pitch of 1.4 with standard reconstruction. The scanning parameters were 120 kV.
In additional to an oral contrast agent, which allows good gastric distention, an intravenous contrast material is essential for complete evaluation of any neoplastic and inflammatory disease of the stomach. We routinely administered 100 ml of nonionic contrast material at a rate of 3 ml/sec. A 70-second delay after initiation of the contrast material injection was used for the portovenous phase of the abdominal images with soft-tissue window.
The CT images of adenocarcinoma, malignant lymphoma and malignant GIST of the stomach were evaluated in a blinded retrospective manner by two staff radiologists. If there were any disagreement, the final interpretation was reached through consensus.
All 89 patients of gastric malignancies who received a definite pathologic diagnosis of gastric adenocarcinoma was 78 patients (87.64%), gastric lymphoma was 4 patients (4.49%) and malignant gastric GIST was 7 patients (7.87%).
CT features of gastric adenocarcinoma ( Figure 1A and 1B ) were focal gastric wall thickening (97.44%), heterogenous enhancement (88.46%), abnormal perigastric fat plane (89.74%), gastric outlet obstruction (46.15%), lymphadenopathy which is above renal hilum (77.55%) and metastasis (52.56%) : liver 42.11%, lung 10.53%, adrenal gland 7.02%, ovary 7.02%, peritoneal seedling 3.51%, omental caking 21.05%, spleen 3.51%, pancreas 3.51% and bone 1.75%.
Figure 1A and 1B : Axial CT scan of a 78 years old man with gastric adenocarcinoma shows focal gastric wall thickening (arrowheads), heterogenous enhancement and abnormal
perigastric fat plane (arrows)
CT findings of gastric lymphoma ( Figure 2A and 2B ) were diffuse gastric wall thickening (75%), homogenous enhancement (50%), normal perigastric fat plane (75%), lymphadenopathy which is below renal hilum (75%) and no gastric outlet obstruction (100%).
Figure 2A and 2B : Axial CT scan of a 76 years old woman with malignant astriclymphoma shows diffuse thickening of gastric wall and homogenous enhancement (arrows)
CT features of malignant gastric GIST ( Figure 3A and 3B )typically appeared large exophytic mass (85.71%), mass containing areas of large mucosal ulceration (57.14%), central necrosis (85.71%), calcification (42.86%), heterogenous enhancement (85.71%), lymphadenopathy (14.29%) and gastric outlet obstruction (0%).
Figure 3A and 3B : Coronal multiplanar reconstruction view from abdomen of a 49 years old woman with malignant gastric GIST shows large exophytic mass which containing areas of large mucosal ulceration (arrows), central necrosis (arrowheads) and heterogeneous enhancement.
In the literature3 revealed the CT features of gastric adenocarcinoma include : a focal area of gastric wall thickening, abnormal perigastric fat, local lymphadenopathy, seeding along the peritoneal ligaments, metastases ; CT features of gastric lymphoma include : diffuse infiltration, wall thickening > 1 cm, circumferential involvement of most of the stomach, homogenous wall-thickening, presence of lymph nodes on either side of the mesenteric vessels ; CT features of malignant gastric GIST include : large heterogenous masses that extent outside the gastric wall, central necrosis and liquefaction, large ulcers and calcifications.
The review by Kim et al. 2, showed that CT findings of gastric lymphoma typically appears as segmental or diffuse wall thickening. The lesions are often indistinguishable from adenocarcinomas. Severe gastric wall thickening, more than one lesion, infrequent gastric outlet obstruction, and lymphadenopathy that extends below the renal hilum favor gastric lymphoma over adenocarcinoma as a diagnosis. CT findings of GISTs that are suggestive of malignancy include large tumor size, an exophytic mass, and a mass containing areas of central necrosis or calcification. Associated lymphadenopathy is uncommon.
Horton and Fishman4 found that in contrast to gastric adenocarcinoma, lymphoma typically involves more than one region of the stomach. Because lymphoma is considered to be a soft tumor, it is less likely to result in gastric outlet obstruction than is gastric adenocarcinoma. Perigastris adenopathy is common in patients with gastric lymphoma as well as in those with gastric adenocarcinoma. However, adenopathy that extends below the renal hila favors gastric lymphoma over adenocarcinoma as a diagnosis. At CT, GISTs vary in size and appearance. When large (> 5 cm), the tumor often appear exophytic and may contain areas of central necrosis or calcification. Associated adenopathy is uncommon, in contrast with gastric adenocarcinoma or lymphoma.
Levy et al.5, reported that gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of the gastrointestinal tract. GISTs most frequently occur in the stomach (70%), followed by the small intestine (20%-30%), anorectum (7%), colon and esophagus. The stomach is the most common location for GISTs, which make up 2%-3% of all gastric tumors. Because GISTs usually involve the outer muscular layer, they have a propensity for exophytic growth. Therefore, the most common appearance is that of a mass arising from the gastric wall and projecting into the abdominal cavity. A peripheral enhancement pattern was present in the majority on intravenous contrast-enhanced CT images. Central areas of low attenuation correspond to hemorrhage, necrosis, or cyst formation. Homogenous enhancement was present in a minority. Calcification is an unusual feature of GISTs. It may occur in a mottled pattern or be present extensively throughout the tumor. CT may also demonstrated evidence of adjacent organ invasion, ascites, omental and peritoneal spread of tumor, or liver metastasis. Metastatic lymphadenopathy is not a feature in patients with GISTs. Gastric adenocarcinoma and lymphoma rarely demonstrate marked exophytic growth. Advanced gastric carcinomas and lymphomas commonly have associated perigastric, hepatoduodenal ligament, and celiac lymphadenopathy, which are not seen in malignant GISTs. Lymphoma may be associated with bulky adenopathy or adenopathy that extends into the lower abdomen and pelvis. Adenopathy is not usually observed in cases of gastric GISTs.
Similarly, Kang et al.1, reported that GISTs can arise anywhere in the gastrointestinal tract. The most common location is the stomach (70% of cases), followed by the small intestine, anorectum, colon and esophagus. In the stomach, the body is the most common site, followed by the fundus and then the antrum. However, because of the exophytic growth pattern of these tumors, some patients remain asymptomatic until the tumor has become quite large. Bowel obstruction is rare. Because they arise from the deep muscularis propria, GISTs frequently have an exophytic or intramural pattern of growth ; endoluminal growth is less common. About 50% of lesions larger than 2 cm. develop focal ulceration of the overlying mucosa because of pressure necrosis. As they enlarge, exophytic GISTs may invade adjacent structures such as the pancreas, colon, or diaphragm. Areas of hemorrhage, necrosis, or cystic degeneration are common, appearing as focal areas of low attenuation. Extensive hemorrhage or necrosis may result in formation of a cavity that communicates with the gastric lumen. In rare cases, clumps of calcifications are seen. Nearly half of patients present with metastatic disease, most commonly to the liver and peritoneum. Lymph node metastasis is infrequent. Occasionally, gastric adenocarcinoma or lymphoma may demonstrate intramural growth and mimic a GISTs. However, advanced gastric carcinomas and lymphomas are usually associated with bulky perigastric or celiac lymphadenopathy, which is rare for GISTs.
The review by Hong et al.6, showed that the CT features of GISTs vary greatly, depending on the size and aggressiveness of the tumor and the time of presentation during the course of the disease. Primary GISTs are typically large, hypervascular, enhancing masses on contrast-enhanced CT scans and are often heterogenous because of necrosis, hemorrhage, or cystic degeneration at the time of presentation. Ulceration and fistulization to the gastrointestinal lumen are also common features of GISTs. Often, tumor vessels can be seen within the tumors. The masses usually displace adjacent organs and vessels, but direct invasion of the adjacent structures is sometime seen with advanced disease. It can be difficult to identify the origin of the mass because of its large size and prominent extraluminal location. Bowel obstruction is rare. Nearly 50% of patients with GISTs present with metastasis. Most metastases of GISTs involve the liver and peritoneum by hematogenous spread and peritoneal seeding, respectively. Unlike gastrointestinal adenocarcinomas, GISTs metastasizing to the lymph nodes are extremely rare.
CT feature is helpful in detection, evaluation and diagnosis of gastric malignancies. CT features of gastric adenocarcinoma typically appear as focal or localized gastric wall thickening, heterogenous enhancement, abnormal perigastric fat plane, gastric outlet obstruction, lymphadenopathy which is above renal hilum and metastases. CT features of gastric lymphoma typically appear as diffuse gastric wall thickening, homogenous enhancement, normal perigastric fat plane, no gastric outlet obstruction and lymphadenopathy which is below renal hilum. CT findings of gastric GIST that are suggestive of malignancy include large exophytic mass which containing areas of large mucosal ulceration, central necrosis, calcification and heterogenous enhancement. Associated lymphadenopathy is uncommon. Gastric outlet obstruction is rare.
1. Kang HC, Menias CO, Gaballah AH, Shroff S, Taggart MW, Garg N, et al. Beyond the GIST : Mesenchymal Tumors of the stomach. Radiographics 2013 ; 33 : 1673-90.
2. Kim JH, Eun HW, Goo DE, Shim CS, Auh YH. Imaging of Various Gastric Lesions with 2D MPR and CT Gastrography Performed with Multidetector CT. Radiographics 2006 ; 26 : 1101-16.
3. Ba-Ssalamah A, Prokop M, Uffmann M, Pokieser P, Teleky B, Lechner G. Dedicated Multidetector CT of the Stomach : Spectrum of Diseases. Radiographics 2003; 23 : 625-44.
4. Horton KM, Fishman EK. Current Role of CT in imaging of the stomach. Radiographics 2003 ; 23 : 75-87.
5. Levy AD, Remotti HE, Thompson WM, Sobin LH, Miettinen M. Gastrointestinal Stromal Tumors : Radiologic Features with Pathologic Correlation 1. Radiographics 2003 ; 23 : 283-304.
6. Hong X, Choi H, Loyer EM, Benjamin RS, Trent JC, Charnsangavej C. Gastrointestinal Stromal Tumor : Role of CT in Diagnosis and in Response Evaluation and Surveillance after Treatment with Imatinib. Radiagraphics 2006 ; 26 : 481-95.