Which of the following statement(s) characterizing gastric lymphoma is/are correct?

a. More than half of gastrointestinal lymphomas occur in the stomach

c. Endoscopic biopsy is positive diagnostically in 90% of cases

 The stomach is the site of more than half of gastrointestinal lymphomas and is the most common organ involved in extranodal lymphomas. Gastric lymphoma is distinctly uncommon in children and young adults. The peak incidence is in the sixth and seventh decades. Radiologic findings are similar to those noted for adenocarcinoma. Endoscopic examination has become the diagnostic method of choice. Endoscopic biopsy, combined with endoscopic brush cytology, provides positive diagnosis in some 90% of cases. When gastric lymphoma is first diagnosed by endoscopic means, evidence of systemic disease should be sought. CT of chest and abdomen (to detect lymphadenopathy), lymphangiography, bone marrow biopsy, and biopsy of enlarged peripheral lymph nodes may all be appropriate. A multimodality treatment program is used in most centers for primary gastric lymphomas, with gastrectomy as the first step in the therapeutic strategy. Increasing numbers of patients are treated with chemoradiation therapy alone. The risk of hemorrhage or perforation was frequently alluded to in the past and has probably been overstated. The risk of perforation in primary gastric lymphomas that are treated with cytolytic agents in unresected patients approximates 5%.