Malignant Tumors of the Stomach


Carcinoma

Carcinoma of the stomach has a dismal prognosis because symptoms are rarely noted until the disease is far advanced. The incidence of gastric cancer varies widely throughout the world. It is very high in Japan, Chile, and parts of eastern Europe, while low in the United States, where for an unknown reason the incidence of the disease has been decreasing. Atrophic gastric mucosa, as in pernicious anemia, especially when associated with intestinal metaplasia, appears to be a predisposing factor. Adenomatous gastric polyps more than 2 cm in diameter frequently contain carcinoma, although it is un clear whether these uncommon large polyps are malignant from the outset or whether they were originally benign. There is also an increased risk of gastric cancer 10 to 20 years following a Billroth II partial gastrectomy for peptic ulcer disease.

Gastric carcinoma can present a broad spectrum of radiographic appearances. Tumor infiltration of the gastric wall may stimulate a desmoplastic response, which produces diffuse thickening, narrowing, and fixation of the stomach wall (linitis plastica pattern). The involved stomach is contracted into a tubular structure without normal pliability. This scirrhous process usually begins near the pylorus and progresses slowly upward, the fundus being the area least involved. Gastric carcinoma can also cause segmental narrowing of the stomach. At an early stage, this may appear as a plaquelike infiltrative lesion along one curvature that progresses to form a constricting lesion similar to that produced by annular carcinoma of the colon.

Polypoid masses larger than 2 cm, partic ularly sessile ones, are often malignant, though many are benign. Irregularity and ulceration suggest malignancy; a stalk, pliability of the wall of the stomach, normal-appearing gastric folds extending to the tumor, and unimpaired peristalsis are signs of benignancy. Mottled, granular calcific deposits in association with a gastric mass suggest mucinous adenocarcinoma of the stomach.

Ulceration can develop in any gastric carcinoma. The radiographic appearance of malignant ulceration runs the gamut from shallow erosions in relatively superficial mucosal lesions to huge excavations within fungating polypoid masses. Signs of malignant ulcer include a lac k of penetration beyond the normal gastric lumen; an abrupt transition between the nodular surrounding neoplastic tissue and the normal mucosa; and adjacent infiltration, rigidity, and mucosal destruction. Although many malignant ulcers show significant healing in response to therapy, there is almost never complete disappearance of the ulcer crater. Endoscopy is indicated if there are radiographic findings suspicious of malignancy or if the ulcer does not heal at the expected rate.

Gastric carcinoma infrequently presents a radiographic pattern of enlarged, tortuous, and coarse gastric folds simulating lymphoma. Unlike most cases of diffuse infiltrating adenocarcinoma, in this form of the disease the gastric volume, pliability, and peristaltic activity remain relatively normal.

In the fundus, carcinoma frequently extends proximally to involve the distal esophagus, producing a radiographic appearance that mimics achalasia.

Following surgery, recurrence of a gastric carcinoma can cause a defect in the gastric remnant, infiltration of the wall with straightening and loss of normal distensibility, or mucosal destruction with superficial ulceration. The major sign of recurrence at the anastomosis is symmetric or eccentric narrowing with local mucosal effacement.

Computed tomography is of major value in the staging and treatment planning of gastric carcinoma as well as in assessing the response to therapy and in detecting recurrence. Carcinoma of the stomach may appear as concentric or focal thickening of the gastric wall or as an intraluminal mass. Obliteration of the perigastric fat planes is a reliable indicator of the extragastric spread of tumor. Computed tomography can demonstrate direct tumor extension to intra-abdominal organs and distant metastases to the liver, ovary, adrenals, kidney, and peritoneum.

Lymphoma

As elsewhere in the bowel, in the stomach lymphoma is a great imitator of both benign and malignant disease. One manifestation of lymphoma of the stomach is a large, bulky polypoid lesion, usually irregular and ulcerated, that can be difficult to differentiate from gastric carcinoma. These polyps can be combined with thickened folds (infiltrative form of lymphoma) or separated by a normal-appearing mucosal pattern, unlike the atrophic mucosal background that is seen with multiple carcinomatous polyps in patients with pernicious anemia. A multiplicity of ulcerated masses suggests lymphoma, as does relative flexibility of the gastric wall.

Thickening, distortion, and nodularity of gastric rugal folds simulating Menetrier’s disease is another pattern of lymphoma of the stomach. If the enlarged rugal folds predominantly involve the distal portion of the stomach and the lesser curvature, or if there is some loss of pliability of the gastric wall, lymphoma is more likely. However, if the process stops at the incisura and spares the lesser curvature, if there is no ulceration or true rigidity, or if excess mucus can be demonstrated, Menetrier’s disease is the probable diagnosis.

Invasion of the gastric wall by an infiltrative type of lymphoma can cause a severe desmoplastic reaction and a radiographic pattern that mimics the linitis plastica appearance of scirrhous carcinoma. Unlike the rigidity and fixation of scirrhous carcinoma, residual peristalsis and flexibility of the stomach wall are often preserved in lymphoma.

Enlargement of the spleen and an extrinsic impression on the stomach by retrogastric and other regional lymph nodes suggest lymphoma as the underlying disorder.

On CT, gastric lymphoma tends to produce bulky masses and a lobulated inner contour of the gastric wall representing thickened gastric rugae. However, gastric lymphoma may also produce smooth, concentric wall thickening or a focal mass simulating adenocarcinoma of the stomach. The demonstration of other signs of lymphoma (splenomegaly, diffuse retroperitoneal and mesenteric lymphadenopathy), when present, suggests the correct histologic diagnosis.

Leiomyosarcoma

Gastric leiomyosarcomas are large, bulky tumors most often found in the body of the stomach. Although originally arising in an intramural location, leiomyosarcomas often present as intraluminal, occasionally pendunculated masses. They frequently undergo extensive central necrosis, causing ulceration and gastrointestinal bleeding. Extensive spread into the surrounding tissues is common (as are metastases to the liver, omentum, and retroperitoneum), and the resulting large exogastric component may suggest an extrinsic lesion. It is frequently impossible to radiographically differentiate a leiomyosarcoma from a benign leiomyoma, though the presence of a large exogastric mass suggests a malignancy.

Computed tomography may demonstrate either the primary intragastric lesion or the large extraluminal component of a leiomyosarcoma. Characteristic findings in tumors of this histologic type are small foci of calcification and well-defined, low-density areas within the mass representing either areas of necrosis and liquefaction or a cystic component to the tumor. Unlike gastric adenocarcinoma or lymphoma, gastric leiomyosarcoma commonly metastasizes to the liver and lung, while spread to regional lymph nodes is unusual.”

stomach · gastric cancer · tumor in stomach ·

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