CT features of gastric lymphoma

Eur. Radiol. 10, 425±430 (2000) Ó Springer-Verlag 2000

European Radiology

Pictorial review CT features of gastric lymphoma K. Gossios1, P. Katsimbri2, E. Tsianos3 1

Department of Radiology, General Hospital of Ioannina, GR-450 01 Ioannina, Greece Section of Oncology, Department of Internal Medicine, School of Medicine, University of Ioannina, GR-451 10 Ioannina, Greece 3 Section of Hepato-Gastroenterology, Department of Internal Medicine, School of Medicine, University of Ioannina, GR-451 10 Ioannina, Greece 2

Received: 11 August 1998; Revision received: 26 March 1999; Accepted: 30 June 1999

Abstract. The gastrointestinal tract is the most frequent site of extranodal involvement by lymphoma and stomach is the most frequently involved. The incidence of gastric lymphoma appears to be rising as that of adenocarcinoma is declining. It produces a spectrum of radiologic appearances and its distinction from adenocarcinoma is difficult since their findings frequently overlap. The aim of this article is to present pictorially a spectrum of CT findings of the gastric lymphoma. Key words: Computed tomography ± Gastric lymphoma

Introduction Primary gastric lymphoma represents 1±5 % of gastric malignancies. More commonly, non-Hodgkin's lymphoma (NHL) involves the stomach as a part of a widespread process, whereas Hodgkin's disease (HD) rarely involves it [1, 2]. When there is gastrointestinal involvement the stomach is more frequently involved in adults accounting for approximately half of the cases, whereas in children the terminal ilium/ascending colon is the most frequent site of involvement [3]. It is more common in males than in females and the median age at the time of diagnosis is 55 years [4]. Primary gastrointestinal lymphomas have an increased incidence in the AIDS population. Although any portion of the gastrointestinal tract can be affected, the stomach and terminal ileum are the most frequent sites of involvement by AIDS-related lymphoma [5]. Patients have epigastric pain, bleeding, early satiety, and fatigue. Lymphoma originates as a submucosal process and deep endoscopic biopsies are usually required for a definite pathologic diagnosis, although they may miss the pathology in up Correspondence to: K. Gossios

to 20 % of cases [6]. Gastric lymphoma has a better prognosis than adenocarcinoma because of its tendency to remain confined to the gastric wall for prolonged periods before tumor spreads. The treatment is mainly surgical for the localized lymphomas considering that eradication of Helicobacter pylori has been preceded, whereas in advanced disease it often includes radiation or chemotherapy alone [7]. Endoscopic studies can be difficult in differentiating lymphoma from benign ulcers, severe gastritis, or even in demonstrating lesions [8, 9]. Imaging studies with barium can show a variety of patterns as infiltrative, polypoid, ulcerative, or nodular lesion which are not pathognomonic [7, 10]. Endoscopic ultrasound can accurately determine the extent of mural invasion and adjacent lymph nodes often having a strikingly hypoechoic appearance. It can also evaluate the therapeutic management [11, 12]. Spiral CT is able to disclose gastric lymphoma as a less enhanced and a markedly thickened wall, and 3D images of the lesion are of excellent quality [13]. Moreover, CT is able to determine the extent of the extraluminal disease which is important for the decision about the need for surgery, radiation, or chemotherapy. Pathologic concepts The gastric NHL are usually of B-cell origin [14] and may range from well-differentiated, superficial process [mucosa-associated lymphoid tissue (MALT)] to highgrade, large-cell lymphoma. The most low-grade B-cell gastric lymphomas arise from MALT, although the stomach normally contains a paucity of lymphoid tissue [15, 16]. Helicobacter pylori has an important role in the development of MALT lymphomas and appears to increase the risk for it. Furthermore, infection with Helicobacter pylori causes chronic gastric inflammation which precedes malignant transformation and might enhance the probability of malignant transformation via chronic stimulation of the lymphoid tissue [16, 17].

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Fig. 1 a, b. Gastric lymphoma. A CT scan after administration of water as an oral agent shows segmental thickening of the wall (arrows) in a the fundus and b body. The outer surface of thickness is lobulated and the inner surface is irregular. The wall lesion has a smooth transition to the normal wall and the fat plane (arrowhead) between the gastric wall and pancreas is preserved Fig. 2 a, b. Gastric lymphoma. A CT scan through the antrum shows a lobulated soft tissue mass (arrow) in the a pre-pyloric region extended to b the duodenum. The tumor is heterogeneous, involves the major part of the lumen, and is confined to the gastrointestinal wall

Fig. 3. Gastric lymphoma. A CT scan through the body after administration of water as an oral agent shows extensive thickening of the gastric wall (arrow) that has locally a soft tissue appearance. The outer surface of the lesion is lobulated and the inner surface is irregular; ascites coexists Fig. 4. Gastric lymphoma. A CT scan through the body and antrum after administration of an oral effervescent agent shows a segmental thickening of the posterior wall (arrow). The inner surface of thickness is lobulated and its transition to the normal wall is smooth. The fat plane between the gastric wall and head of pancreas is preserved

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CT examination Gastric wall thickness can be evaluated by adequately filling its lumen with contrast agent. Among the agents which have been used, water is now widely used, although in severely ill patients air is preferable. Oral ingestion of 600±800 ml of pure tap water or 2 g of gasproducing agent before scanning are sufficient for optimal distention of the stomach. Intravenous administration by bolus injection of 100 ml of nonionic contrast material at a rate of 2.5 ml/s for the first 50 ml and the residual 50 ml at a rate of 1 ml/s has a result of better delineation of the gastric wall or tumor enhancement. The first scan is obtained 40 s after the start of intravenous contrast administration. Scanning is usually performed with 5- or 10-mm slice thickness and interval and with 5-mm slices through the lesion [18, 19, 20, 21, 22, 23]. Dynamic studies and current technology demonstrate the multilayered patterns of the normal gastric wall in 58.4 %, most commonly two-layered and any focal destruction of this pattern [18, 19, 20, 21, 22, 23]. Evaluation of the perigastric tumor invasion depends on its location and size, and patient's position; therefore, additional images can be obtained in prone and decubitus position.

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Gastric wall pattern Marked gastric wall thickening is the leading finding of CT in patients with gastric lymphoma. The wall thickness is greater than 1 cm tending to produce bulky masses (mean thickness ranges from 2.9 to 5 cm) [7, 24]. Thickening affects the wall of the entire stomach in 50 % of cases; otherwise, the area of the predominant involvement is antrum, body, and fundus. Lesions in the proximal part of the stomach often are of the segmental form, whereas antral involvement is of the diffuse form. Wall thickening typically involves more than half of the circumference of the gastric lumen and more than one region of the stomach is involved. These findings demonstrate the submucosal spread of gastric lymphoma (Figs. 1, 2) [24, 25, 26]. The lymphomatous gastric wall may have no uniform attenuation values containing hypodense areas below the inner surface of lymphoma. They could be due to necrosis, hemorrhage, submucosal edema, or infarction, but the exact cause of the heterogeneity on CT has not been determined [25]. The outer gastric margin is usually smooth or lobulated, whereas the inner gastric wall is frequently irregular in contour representing distortion of the thickened gastric rugae (Figs. 3, 4). The CT appearance of the gastric wall alone is not diagnostic for lymphoma, and data as sensitivity±specificity of CT in the diagnosis are not available in the known literature. Evaluation of perigastric area Lymphadenopathy is not necessarily present in cases of primary gastric lymphoma [26], but most patients have

b Fig. 5 a, b. Gastric lymphoma. a A CT scan through the fundus after administration of water as an oral agent shows a marked circumferential thickening of the gastric wall (arrow). The thickness is equal with smooth inner and outer surfaces. Enlarged lymph nodes in the gastrosplenic ligament are present (arrowhead). b A more caudal scan through the body shows the wall thickening to be lobulated and extensive lymphadenopathy in the gastrohepatic ligament to be present as well (arrowhead)

regional lymphadenopathy in the gastrohepatic and gastrocolic ligaments or greater omentum. The widespread lymphadenopathy in the mesentery, retroperitoneum, or elsewhere in the abdomen should suggest the diagnosis of lymphoma [27]. Lymphadenopathy usually indicates disseminated disease (Fig. 5). The fat plane between the outer gastric wall and adjacent organs is usually preserved, but it could be obliterated indicating contiguous spread of disease (see Figs. 1, 10) [25]. It frequently invades the pancreas, but extension to the spleen, transverse mesocolon, and pleura is also found. Perforation is a complication following chemotherapy and may be clinically silent. Computed tomography can visualize free air as well as fistulization by demonstrating low-density collections in the lesser sac or subphrenic space [28].

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Fig. 6. Hypertrophic gastritis. A CT scan through the fundus after administration of water as an oral agent shows extensive thickening of the gastric wall. The inner surface of thickness is lobulated and at least one small faint hypodense area is cited below it (arrow) Fig. 7. Hypertrophic gastritis. A CT scan through the body and antrum after administration of an oral effervescent agent in a 22year-old woman who lost 20 kg of weight in 2 months and complained of epigastric pain. There is extensive circumferential thickening of the gastric wall with smooth inner surface and narrowing of the gastric lumen (arrows) Fig. 8. Gastric leiomyoma. A CT scan through the antrum shows a lobulated soft tissue mass in the pre-pyloric region (arrowhead) which involves the major part of the lumen and is confined to the gastric wall (see Fig. 2) Fig. 9. Gastric cancer. A CT scan through the fundus and body after administration of water as oral agent shows a thickening of posterior wall (arrow). The inner and outer surfaces of thickness and its transition to the normal wall are smooth. An enlarged lymph node is in the gastrohepatic ligament

The individual CT features of lymphoma and adenocarcinoma, a much more common malignant neoplasm of the stomach, overlap. Computed tomography cannot reliably differentiate them based on wall thickness, its distribution, or the pattern of its contour alone (Fig. 9) [24]. An extragastric CT feature highly suggestive of gastric lymphoma is the preservation of the fat plane between the stomach and adjacent organs which is more common in patients with gastric lymphoma than with adenocarcinoma. The most reliable differential finding is the distribution of lymphadenopathy. Retroperitoneal lymphadenopathy beneath the level of the renal hilum more likely indicates lymphoma than adenocarcinoma [25]. Moreover, splenomegaly, when present, is another sign suggestive of gastric lymphoma. Although the gastric wall is thickened in severe peptic gastritis or other benign inflammatory disease, it may be less than in neoplasms [24].

Differential diagnosis

Management

Differential diagnosis of gastric lymphoma includes adenocarcinoma and benign inflammatory processes that cause gastric wall thickening such as gastritis, Crohn's disease, and peptic ulcer disease (Figs. 6, 7, 8).

Subtotal gastrectomy usually followed by chemotherapy has been the treatment of choice for many years in patients with localized lymphoma, and reported 5-year survival rates range from 40 to 60 % [28]. Presently, be-

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Fig. 10 a, b. Gastric lymphoma. a Before treatment. A CT scan through the body and antrum shows a circumferential marked thickening of gastric wall (arrow). The inner surface of thickness is smooth and lobulated and the fat plane (arrowhead) between the gastric wall and pancreas is preserved. b After chemotherapy. The gastric wall thickness has been reduced Fig. 11 a, b. Gastric lymphoma. a Before treatment. A CT scan shows considerable soft tissue wall thickening of the body (open arrow). The inner surface of thickness is markedly irregular. The fat of gastrohepatic ligament is blurred with enlarged lymph nodes (arrowhead). b After chemotherapy. The lesion has been markedly reduced

cause of the rising evidence of relation between gastric malignant lymphoma of the mucosa-associated lymphoid tissue (MALT) and Helicobacter pylori, antibiotic treatment to eradicate the Helicobacter pylori infection has been proposed. Such treatment has led to suppression of many gastric MALT lymphomas [29]. Chemotherapy alone has increasing use in patients with advanced disease and preoperative radiographic evidence of nodal involvement [28]. Some of them treated with chemotherapy may show marked regression of lymphomatous lesions in the stomach [30] (Figs. 10, 11); however, chemotherapy may also lead to ulceration or perforation of these lesions with the development of massive upper gastrointestinal bleeding or peritonitis [30].

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