Updated: Feb 26, 2009
Gastric carcinoma is the most common cancer in the world after lung cancer and is a major cause of mortality and morbidity. Though a marked reduction has been observed in the incidence of gastric carcinoma in North America and Western Europe in the last 50 years, 5-year survival rates are less than 20%, as most patients present late and are unsuitable for curative, radical surgery.
The accepted pathway involves transitions from gastritis, to gastric atrophy, to metaplasia, to dysplasia, and, finally, to cancer.
Several dietary and environmental factors may influence this pathway.
Several precancerous conditions are recognized:
Adenocarcinomas account for approximately 95% of all malignant gastric neoplasms. The remaining 5% of tumors are lymphomas, leiomyosarcomas, carcinoids, or sarcomas.
Gastric adenocarcinomas are divided into 2 types:
With gastric carcinomas, advanced lesions will have already invaded the muscularis propria. They are associated with metastases to regional lymph nodes or to local or distant structures.
Early gastric lesions are confined to the mucosa or submucosa. Patients with these tumors have a 5-year survival rate of 90%. Most reports are from Japan as a result of mass screening in that country.
Before 1950, most gastric tumors detected were located in the antrum. Since then, the location has gradually shifted from the antrum to the body and fundus because of the rapidly increasing incidence of carcinoma in the gastric cardia and lower esophagus. Today, 30% of gastric lesions are found in the antrum, 30% are in the body, and 40% are in the fundus and cardia.
The incidence decreased from 33 cases per 100,000 population in 1930 to 3.7 cases per 100,000 population in 1990. In 1996, about 22,800 new cases of gastric adenocarcinoma occurred. In Western countries, the incidence of carcinoma of the cardia has increased rapidly in the last 20 years, in contrast to the decline in gastric cancer as a whole, particularly in tumors of the body and antrum.
Worldwide, gastric adenocarcinoma is the second most common cancer (second to lung cancer). The global incidence of gastric cancer varies 10-fold. The highest incidence (>30 cases per 100,000 population) is in Japan, Russia, China, South America, and Eastern Europe. The lowest incidence ( <3.7 cases per 100,000 population) is in North America, Western Europe, Australia, and New Zealand.
Gastric carcinoma is 2 times more common in men than in women. Moreover, carcinoma of the cardia of the stomach is up to 7 times as common in men as in women.
Gastric carcinoma has a peak incidence in those aged 50-70 years; however, approximately 5% of patients with gastric cancer are younger than 35 years, and 1% are younger than 30 years. Younger patients have more aggressive lesions with a worse prognosis.
The stomach consists of the cardia (adjacent to the gastroesophageal junction), the fundus, the body, the antrum, and the pylorus. The fundus is dome-shaped and extends above and to the left of the cardia, toward the left hemidiaphragm. The body extends from the fundus to the lower end of the lesser curve, known as the incisura angularis. The antrum extends from the incisura to the pyloric canal.
The stomach is lined by peritoneum. The lesser omentum and greater omentum are double layers of peritoneum that extend from the lesser curve and greater curve, respectively.
The right and left gastric, right and left gastroepiploic, and short gastric arteries supply the stomach. These arteries originate from all 3 branches of the celiac trunk. The venous drainage is into the portal vein or one of its branches. The lymphatic drainage is into the celiac lymph nodes surrounding the celiac trunk.
Presentation
Most patients present with advanced disease because they are often asymptomatic in the earlier stages. Common presenting features include epigastric pain, bloating, early satiety, nausea, vomiting, dysphagia, anorexia, weight loss, and upper GI bleeding (hematemesis, melena, iron deficiency anemia, positive results with fecal occult blood tests).
Differential diagnosis
Because peptic ulcers and gastritis cause similar findings, diagnosis is often delayed. Jaundice and hepatomegaly may be due to hepatic metastases. Pelvic masses may be the result of ovarian metastases (Krukenberg tumors).
Prognosis and staging
The prognosis is related to the stage of the disease at the time of diagnosis and to the histologic grade of the carcinoma.1
Pathologic staging is based on tumor stage, nodal stage, and metastasis stage (TMN).
Staging and 5-Year Survival Rates
| Stage | TNM Stage | 5-Year Survival |
| 1 | T1N0M0, T1N1M0, or T2N0M0 | 88% |
| 2 | T1N2M0, T2N1M0, or T3N0M0 | 65% |
| 3a | T2N2M0, T3N1M0, or T4N0M0 | 35% |
| 3b | T3N2M0 | 35% |
| 4 | T4N1-3M0, TxN3M0, or TxNxM1* | 5% |
*Tx indicates any T stage; Nx, any N stage.
Endoscopy with biopsy has a sensitivity of 95%. Multiple biopsy specimens are needed to avoid sampling errors. Endoscopy is less reliable in the diagnosis of scirrhous tumors (35-70%). False-negative biopsy results may delay diagnosis.
Single-contrast barium studies have an overall sensitivity of 75%, but double-contrast barium examinations have a sensitivity of 90-95% in the detection of gastric cancer, comparable to endoscopy.
| Colon Cancer, Adenocarcinoma | Gastritis, Atrophic |
| Crohn Disease | Gastritis, Chronic |
| Esophageal Cancer | Gastrointestinal Stromal Tumors -
Leiomyoma/Leiomyosarcoma |
| Gastric Cancer | Peptic Ulcer Disease |
| Gastric Stromal Tumors | |
| Gastric Ulcer | |
| Gastritis, Acute |
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:
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.
Special considerations
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.
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.
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.
CT scans may show the following:
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.
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.
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).
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.
For accuracy rates with CT, see Degree of Confidence in the Ultrasound section.
CT has several pitfalls.
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.
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.
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:
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.
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.
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.
Inoperable obstructing gastric carcinomas can be treated with a covered metallic stent as an alternative to palliative surgery, especially for frail patients who are unable to tolerate surgery.6
Stents are also used to treat recurrent tumors that obstruct the gastrojejunal anastomosis. Further surgery is often of little value in patients with this condition.
Complications from stents include stent migration, obstruction, perforation, and bleeding.
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gastric carcinoma, adenocarcinoma of the stomach, gastric adenocarcinoma, gastric cancer, stomach cancer, stomach carcinoma, gastric lymphoma, gastric leiomyosarcoma, gastric carcinoid, gastric sarcoma
Isaac Hassan, MB, ChB, FRCR, DMRD, Former Senior Consultant Radiologist, Department of Radiology, St Bernard's Hospital, Gibraltar
Isaac Hassan, MB, ChB, FRCR, DMRD is a member of the following medical societies: American Roentgen Ray Society and Royal College of Radiologists
Disclosure: Nothing to disclose.
John L Haddad, MD, Clinical Associate Professor, Department of Radiology, Weill Medical College of Cornell University; Director of Body MRI, Department of Radiology, Methodist Hospital in Houston
John L Haddad, MD is a member of the following medical societies: American College of Radiology, American Medical Association, and Radiological Society of North America
Disclosure: Nothing to disclose.
Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand
Disclosure: Nothing to disclose.
David Andrew Nicholson, BM, BS, FRCR, Honorary Lecturer, Department of Radiology, University of Manchester; Consultant Gastrointestinal Radiologist, Department of Radiology, Hope Hospital, Salford Royal Hospital NHS Trust
Disclosure: Nothing to disclose.
Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute
Robert M Krasny, MD is a member of the following medical societies: American Roentgen Ray Society and Radiological Society of North America
Disclosure: Nothing to disclose.
Eugene C Lin, MD, Consulting Radiologist, Virginia Mason Medical Center; Clinical Assistant Professor of Radiology, University of Washington School of Medicine
Eugene C Lin, MD is a member of the following medical societies: American College of Nuclear Medicine, American College of Radiology, Radiological Society of North America, and Society of Nuclear Medicine
Disclosure: Nothing to disclose.
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