Gastric lymphoma

Overview
Primary gastric lymphoma (lymphoma that originates in the stomach itself) is an uncommon condition, accounting for less than 15% of gastric malignancies and about 2% of all lymphomas. However, the stomach is a very common extranodal site for lymphomas (lymphomas originating somewhere else with metastasis to stomach) ; it is also the most common source of lymphomas in the gastrointestinal tract

Clinical presentation
Primary gastric lymphoma usually affects the elderly (with peak incidence in the sixth decade of life) and presenting symptoms include epigastric pain, early satiety, fatigue and weight loss.

Diagnosis
These lymphomas are often difficult to differentiate from gastric adenocarcinoma. The lesions are usually ulcers with a ragged, thickened mucosal pattern on contrast radiographs.

The diagnosis is typically made by biopsy at the time of endoscopy. Several endoscopic findings have been reported, including solitary ulcers, thickened gastric folds, mass lesions and nodules. As there may be infiltration of the submucosa, larger biopsy forceps, endoscopic ultrasound guided biopsy, endoscopic submucosal resection, or laparotomy may be required to obtain tissue.

Imaging investigations including CT scans or endoscopic ultrasound are useful to stage disease. Hematological parameters are usually checked to assist with staging and to exclude concomitant leukemia. An elevated LDH level may be suggestive of lymphoma.

Histopathology
The majority of gastric lymphomas are non-Hodgkin's lymphoma of B-cell origin. These tumors may range from well-differentiated, superficial involvements (MALT) to high-grade, large-cell lymphomas.

Other lymphomas involving the stomach include mantle cell lymphoma and T-cell lymphomas which may be associated with enteropathy; the latter usually occur in the small bowel but have been reported in the stomach.

Risk factors
Risk factors for gastric lymphoma include the following:
 * Helicobacter pylori
 * Long-term immunosuppressant drug therapy
 * HIV infection

Treatment
Diffuse large B-cell lymphomas of the stomach are primarily treated with chemotherapy with CHOP with or without rituximab being a usual first choice.

Antibiotic treatment to eradicate H. pylori is indicated as first line therapy for MALT lymphomas. About 60% of MALT lymphomas completely regress with eradication therapy. Second line therapy for MALT lymphomas is usually chemotherapy with a single agent, and complete response rates of greater than 70% have gain been reported.

Subtotal gastrectomy, with post-operative chemotherapy is undertaken in refractory cases, or in the setting of complications, including gastric outlet obstruction.