Radiography
Findings
Early gastric cancer
Double-contrast barium upper GI examination is widely recognized as the radiologic technique of choice for diagnosing early gastric cancers. These lesions are confined to the mucosa or submucosa and are classified into 3 types:
- Type I lesions are elevated and protrude more than 5 mm into the lumen.
- Type II tumors are superficial lesions that are elevated (IIa), flat (IIb), or depressed (IIc).
- Type III early gastric cancers are shallow, irregular ulcers surrounded by nodular, clubbed mucosal folds.
In Western counties, early gastric cancers account for only 5-20% of all gastric cancers. In Japan, they represent 25-46% owing to the population-screening program that was implemented to combat the high incidence of the disease.
Advanced carcinoma
Gastric carcinomas are occasionally seen on plain abdominal radiographs as abnormalities in the gastric contour or as soft-tissue masses indenting the gastric contour. Rarely, mucin-producing carcinomas may show areas of punctate calcification.
On barium studies, gastric carcinomas may be polypoidal, ulcerative, or infiltrating lesions.
Polypoid carcinomas are lobulated masses that protrude into the lumen (see Image 2). They may contain 1 or more areas of ulceration.
Polypoid carcinoma of the body of the stomach.
With ulcerated carcinomas, an irregular crater is located in a rind of malignant tissue. Seen en face, tumor nodules may be in the adjacent mucosal folds; the mucosal folds that converge to the edge of the ulcer may be blunted, nodular, or clubbed from tumor infiltration. Seen in profile, these lesions are intraluminal, whereas benign ulcers project beyond the contour of the stomach. The radiating folds associated with a benign ulcer are regular and extend close to the ulcer margins (see Image 3). Endoscopy and biopsy are generally required to confirm or rule out malignancy in most cases of gastric ulcers.
Gastric ulcer with symmetrical, radiating mucosal folds. At histologic evaluation, no evidence of malignancy was observed.
Infiltrating carcinoma involving the greater curve of the stomach.
Infiltrating carcinomas result in irregular narrowing of the stomach, with nodularity or spiculation of the mucosa (see Image 4).
Special considerations
- Scirrhous carcinomas typically cause irregular narrowing and rigidity of the stomach, giving rise to the typical linitis plastica, or "leather bottle" appearance (see Image 5). Although some are lobulated lesions in the fundus or body, others consist of thickened, irregular mucosal folds and nodularity without significant narrowing.
Linitis plastica.
- Carcinomas of the cardia are often missed during single-contrast examinations. In double-contrast studies, normal anatomic landmarks are obliterated and replaced by a plaquelike lesion with nodularity or ulceration. The distal esophagus is often involved (see Images 6-7).
Extensive carcinoma involving the cardia and fundus.
- Submucosal spread of tumors may result in pseudo-achalasia or secondary achalasia with tapered, beaklike narrowing of the distal esophagus (see Image 8) and infiltration of the gastric cardia (see Image 9).
Secondary or pseudoachalasia due to infiltrating carcinoma of the cardia.
Note malignant infiltration of the cardia (same patient as in Image above).
Degree of Confidence
Single-contrast studies have a sensitivity of 70%, but double-contrast examinations have a sensitivity of 90%.
Equivocal lesions should always be confirmed or ruled out by means of endoscopy and biopsy.
False Positives/Negatives
The appearance of gastric carcinomas on barium studies must be distinguished from the appearances of benign gastric ulcers and polyps, gastric lymphomas, and focal gastritis. Malignant stromal tumors may also cause confusion. Although linitis plastica is usually caused by gastric carcinoma, it can also be caused by metastatic breast cancer.
In rare cases, radiation therapy, Crohn disease, tuberculosis, sarcoidosis, and syphilis may simulate gastric carcinoma, and primary esophageal adenocarcinoma may invade the stomach. Gastric varices and inadequate distention may mimic tumors of the gastric fundus.
Computed Tomography
Findings
CT is used preoperatively primarily to determine the stage and extragastric spread of a gastric carcinoma. This information is vital in deciding between palliative surgery and curative radical surgery (ie, identifying patients who would not benefit from radical surgery). Additionally, CT is used to monitor a patient's response to treatment.2,3,4
Detection of gastric carcinoma is improved by using thin-section sequences and helical or multidetector-row CT. When thin collimation is used, near-isotropic imaging of the stomach is possible, allowing high-quality multiplanar reformation and 3-dimensional reconstruction of gastric images. An intravenous contrast medium is used, along with water or gas as a negative intraluminal agent (see Image 10). Prone views improve visualization of tumors of the cardia and distal stomach.
The stomach is distended by using water as a negative intraluminal contrast agent. Results of this examination are normal.
Helical scanning allows for a biphasic technique. The early arterial phase is used to assess enhancement of the gastric wall; the later portal venous phase is used to assess the liver parenchyma for metastases.
CT scans may show the following:
- Polypoidal mass with or without ulceration
- Focal wall thickening with mucosal irregularity or ulceration
- Wall thickening with the absence of normal mucosal folds (infiltrative lesions)
- Focal infiltration of the gastric wall (see Image 11)
Carcinoma of the lesser curve. Note the focal mural thickening due to a tumor plaque.
- Variable thickening of the wall and marked contrast enhancement (typical of scirrhous lesions)
- Mucinous carcinomas, which have low attenuation due to their high mucin content and which may contain calcification
T staging
The depth of tumor invasion is not accurately assessed with CT.
Tumor invasion of the perigastric fat is seen as soft-tissue stranding. Tiny 4- to 8-mm nodules may be observed. These may coalesce into sheets of tumor in advanced cases.
Direct extension of the tumor is relatively common. The pancreas is invaded via the lesser sac; the transverse colon, via the gastrocolic ligament; and the liver, via the gastrohepatic ligament.
Longitudinal spread to the distal esophagus occurs in as many as 60% of patients with carcinoma of the cardia (see Images 12-13). However, the duodenum is involved in only 5-20% of antral carcinomas.
Carcinoma of the cardia. Note the liver metastasis.
Tumor extension to the distal esophagus (same patient as in Image above).
Overall, the accuracy of determining the T-stage with CT is approximately 66%. N staging
Lymph node metastases occur in approximately 80% of patients with gastric cancer (see Images 15-17). The frequency is related to the size and depth of the tumor; local perigastric nodes are involved first, followed by the regional (celiac, hepatic, left gastric, splenic) and distant (left supraclavicular and axillary) nodes.
Celiac-axis nodes measure 8-12 mm and are from carcinoma of the cardia. Note the irregular liver metastasis and adjacent rounded cyst.
Carcinoma of the body of the stomach associated with regional lymphadenopathy and ascites.
CT depicts 75% of nodes larger than 5 mm in diameter, but it does not depict tumor in normal-sized nodes. CT is not useful in distinguishing between enlarged nodes due to reactive changes and those due to tumor.
The local nodes (N1) are located in the prepyloric region and in the gastrocolic and gastrohepatic ligaments. These nodes are removed by performing the standard gastrectomy procedure. The regional nodes (N2), located in the porta hepatis, hepatoduodenal ligament, and peripancreatic region, are not removed by the gastrectomy procedure; thus, their detection is more important.
In the new TNM tumor classification system, nodal staging is related to the number of regional nodes involved in the perigastric group and around the celiac axis. Enlarged nodes elsewhere (eg, in the retroperitoneum and mesentery) are classified as distant metastases. N1 indicates 1-4 nodes; N2, 7-15 nodes; and N3, more than 15 nodes.
M staging
Because the portal vein drains the stomach, the liver is the most common site for hematogenous metastases (see Image 12, Image 15). Less common sites are the lungs (see Image 19), adrenal glands, and kidneys. Bony and cerebral metastases are uncommon.
Intraperitoneal and omental metastases are common in advanced gastric cancer. They consist of nodules, localized fluid collections, and irregular thickening and stranding of the mesentery and omentum (see Images 17-18).
Carcinoma of the body of the stomach associated with regional lymphadenopathy and ascites.
Extensive mesenteric, omental, and peritoneal metastases (same patient as in Image above).
Ascites (see Images 16-18) and small-bowel obstruction may occur.
Gastric carcinoma is the most common primary tumor to metastasize to the ovaries. These ovarian metastases are usually bilateral and are known as Krukenberg tumors.
Degree of Confidence
For accuracy rates with CT, see Degree of Confidence in the Ultrasound section.
CT has several pitfalls.
- A pseudo-mass as a result of a normal gastroesophageal junction may be seen.
- Underdistention of the stomach may simulate wall thickening.
- T2 and T3 lesions may be difficult to distinguish.
- Loss of a fat plane between the gastric wall and the left lobe of the liver may be seen.
- Loss of a fat plane between the tumor and pancreas may be due to an inflammatory reaction.
- In cachectic patients, a loss of fat planes may simulate direct organ invasion.
- Small nodes may contain tumor.
- Large nodes may be due to inflammatory causes.
- Perigastric nodes may not be observed if the stomach is not well distended.
- CT may fail to depict tiny omental and peritoneal deposits.
- Small pelvic deposits may be overlooked.
Magnetic Resonance Imaging
Findings
Recent studies in which a breath-hold fast-imaging technique and water were used have shown accuracy rates comparable to those of helical biphasic CT scanning. The fast-imaging technique was superior to CT in detecting serosal invasion.
Degree of Confidence
In T staging, the accuracy of MRI is 73%, compared with 67% for CT. In N staging, the accuracy of MRI is 55%, compared with 59% for CT.
MRI is limited by respiratory and peristaltic artifacts, the lack of suitable oral contrast media, and higher cost, as compared with CT.
Ultrasonography
Findings
The primary role of transabdominal ultrasonography (US) is to detect liver metastases. These metastases are usually hyperechoic, but they may be hypoechoic. CT scanning and endoscopic ultrasonography (EUS) are complementary. CT scanning is used first to stage the gastric carcinoma; if no metastases and no invasion of local organs are shown, EUS is used to refine the local stage. The depth of tumor invasion is not accurately assessed with CT, and the investigation of choice for this indication is EUS.
Gastric carcinomas are occasionally identified during US of the upper abdomen.
EUS has improved the accuracy of local staging of gastric carcinomas. Its role is to assess the depth of local invasion and the presence or absence of perigastric nodes. Unlike CT and MRI, EUS can depict individual layers of the gastric wall with a rotating high-frequency probe inserted via an endoscope. EUS is limited to an area 5 cm from the probe. It cannot be used to assess distant metastases or nodes more than 5 cm away from the probe.
The gastric wall is visualized as 5 concentric bands:
- Mucosa - echogenic
- Muscularis mucosa - hypoechoic
- Submucosa - echogenic
- Muscularis propria - hypoechoic
- Serosa – echogenic
A gastric tumor is demonstrated as a hypoechoic mass with varying mural invasion. Its depth may be overestimated, because of the inflammatory response around the tumor, or it may be underestimated, because of microscopic spread.
With T1 tumors, wall thickening is limited to the mucosa and submucosa. Regarding N staging, involved nodes are rounder and more hypoechoic than normal nodes.
Degree of Confidence
In the detection of liver metastases, sensitivities as high as 85% have been reported.Overstaging is due to the peritumoral inflammatory response.
In T staging, EUS is 89-92% accurate, and CT is 43-65% accurate; however, the accuracy of CT increases with the use of the helical biphasic technique. In N staging, EUS is 60-85% accurate, and CT is 48-70% accurate. Inflammation may cause enlarged nodes. EUS has a high specificity (90%) but low sensitivity (53-80%) because it has a range of 5 cm from the gastric wall for nodes of normal size; thus, it does not permit assessment of the full extent of lymphadenopathy. Involved small nodes are not detected.
Intraoperative US and laparoscopy have an accuracy of 81% in T staging and an accuracy of 93% in N staging; however, the necessary equipment and expertise are not widely available.
Nuclear Imaging
Findings
Fluorodeoxyglucose–positron emission tomography (FDG-PET) may be useful in the staging and postoperative assessment of gastric carcinomas. FDG-PET depicts the primary tumor, but involved perigastric lymph nodes are not identified separately from the primary tumor. Thus, the role of PET is limited in staging. The use of combined PET-CT scanning may improve diagnostic accuracy.5
Indium-111 (111 In) labeled monoclonal antibody has been used for intraoperative imaging to detect nodes, with an accuracy of 72%.
FDG-PET may be useful in evaluating patients with recurrent gastric cancer; findings can help localize the disease when CT findings are not diagnostic. Imaging evaluation with PET may also impact the clinical management of patients with recurrent gastric cancer.
More on Gastric Carcinoma |
| Overview: Gastric Carcinoma |
 Imaging: Gastric Carcinoma |
| Follow-up: Gastric Carcinoma |
| Multimedia: Gastric Carcinoma |
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Further Reading
Related eMedicine topics
Gastric Cancer
Gastric Stromal Tumors
Esophagogastroduodenoscopy
Colon Cancer, Adenocarcinoma
Crohn Disease
Esophageal Cancer
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Gastritis, Acute
Gastritis, Atrophic
Gastritis, Chronic
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Clinical guidelines
Surgical Treatment of Gastric Cancer
Neoadjuvant or Adjuvant Therapy for Resectable Gastric Cancer
Clinical trials
Irofulven in Treating Patients with Recurrent or Metastatic Gastric Cancer
A Study of 5-FUci Versus CPT-11 Plus CDDP Versus S-1 Alone in Advanced Gastric Cancer
Keywords
gastric carcinoma, adenocarcinoma of the stomach, gastric adenocarcinoma, gastric cancer, stomach cancer, stomach carcinoma, gastric lymphoma, gastric leiomyosarcoma, gastric carcinoid, gastric sarcoma
