Inclusion Criteria:

1. histologically proven diagnosis of CD20-positive marginal zone B-cell lymphoma of MALT type arisen at any extranodal site
2. any stage (Ann Arbor I-IV)
3. either de novo, or relapsed disease following local therapy (including surgery, radiotherapy and antibiotics for H. pylori-positive gastric lymphoma)
4. no evidence of histologic transformation to a high grade lymphoma
5. measurable or evaluable disease
6. age > 18
7. life expectancy of at least 1 year
8. ECOG performance status 0-2
9. no prior diagnosis of neoplasm within 5 years, except cervical intraepithelial neoplasia type 1 (CIN1) or localized non-melanomatous skin cancer
10. no prior chemotherapy
11. no prior immunotherapy with any anti-CD20 monoclonal antibody
12. no prior radiotherapy in the last 6 weeks
13. no corticosteroids during the last 28 days, unless prednisone chronically administered at a dose <20 mg/day for indications other than lymphoma or lymphoma-related symptoms
14. no evidence of clinically significant cardiac disease, as defined by history of symptomatic ventricular arrhythmias, congestive heart failure or myocardial infarction within 12 months before study entry
15. no evidence of symptomatic central nervous system (CNS) disease
16. no impairment of bone marrow function (WBC >3.0x109/L, ANC >1.5x109/L, PLT >100x109/L), unless due to lymphoma involvement
17. no major impairment of renal function (serum creatinine <1,5x upper normal) or liver function (ASAT/ALAT <2,5 upper normal, total bilirubin <2,5x upper normal), unless due to lymphoma involvement
18. no evidence of active opportunistic infections
19. no known HIV infection
20. no active HBV and/or HCV infection
21. no pregnant or lactating status
22. appropriate contraceptive method in women of childbearing potential or men
23. absence of any psychological, familial, sociological or geographical condition potentially hampering compliance with the study protocol and follow-up schedule; those conditions should be discussed with the patient before registration in the trial
24. informed consent must be given according to national/local regulations before randomization