ESSENTIALS OF DIAGNOSIS
Symptoms of dyspepsia, weight loss, or anemia.
Variable abnormalities on upper gastrointestinal series or endoscopy including thickened folds, ulcer, mass, or infiltrating lesions; diagnosis established by endoscopic biopsy.
Abdominal CT and EUS required for staging.
Gastric lymphomas may be primary (arising from the gastric mucosa) or may represent a site of secondary involvement in patients with nodal lymphomas. Distinguishing advanced primary gastric lymphoma with adjacent nodal spread from advanced nodal lymphoma with secondary gastric spread is essential because the prognosis and treatment of primary and secondary gastric lymphomas are different. Primary gastric lymphoma is the second most common gastric malignancy, accounting for 3–5% of gastric cancers. More than 95% of these are non-Hodgkin B-cell lymphomas mainly consisting of either mucosa-associated lymphoid tissue (MALT)-type lymphoma and diffuse large B-cell lymphoma. Gastric T-cell lymphoma, which is associated with HTLV-1 infection, is rare and makes up 7% of primary gastric lymphomas.
Infection with H pylori is an important risk factor for the development of primary gastric lymphoma. Chronic infection with H pylori causes an intense lymphocytic inflammatory response that may lead to the development of lymphoid follicles. Over 90% of low-grade primary gastric MALT-type lymphomas are associated with H pylori infection. It is hypothesized that chronic antigenic stimulation may result in a monoclonal lymphoproliferation that may culminate in low-grade or high-grade lymphoma.
CLINICAL FINDINGS & STAGING
The clinical presentation and endoscopic appearance of gastric lymphoma are similar to those of adenocarcinoma. Most patients have abdominal pain, weight loss, or bleeding. Patients with diffuse large B-cell lymphoma are more likely to have systemic symptoms and advanced tumor stage. At endoscopy, lymphoma may appear as an ulcer, mass, or diffusely infiltrating lesion. It tends to have horizontal infiltration as opposed to the vertical extension seen in adenocarcinoma. The diagnosis is established with endoscopic biopsy; FNA is not adequate. Since the disease can be multifocal, biopsies of both suspicious and normal-appearing areas are recommended. Biopsy specimens should be tested for H pylori and, if positive, for t(11;18) via PCR or FISH. EUS is the most sensitive test for determining the level of invasion and presence of perigastric lymphadenopathy and should be performed for accurate staging, if available. All patients should undergo staging with CT scanning of chest, abdomen, and pelvis. For gastric MALT lymphomas, the Lugano staging system is most frequently used. Stage I is confined to the gastrointestinal tract, stage II involves local or regional lymph nodes, stage IIE has invasion of adjacent organs or tissues, and stage IV has distant metastases. There is no stage III. For patients with diffuse large B-cell lymphomas involving the stomach, combination PET-CT imaging, bone marrow biopsy with aspirate, tumor lysis laboratory tests, and hepatitis B and HIV serologies also may be required for staging and treatment planning (see Chapter 13).