OBJECTIVES: I. Determine the efficacy of cladribine (2-chlorodeoxyadenosine; 2-CdA) as treatment for mantle cell lymphoma (MCL) either as initial therapy or for relapsed/refractory disease. II. Determine by flow cytometry immunophenotyping of blood lymphocytes the number of patients with peripheral blood involvement at the time of diagnosis and compare the presence or absence of peripheral blood involvement with response data. III. Detect rearrangements involving the bcl-1 gene and immunoglobulin heavy chain locus by molecular techniques (e.g., polymerase chain reaction, Southern blotting, or in situ hybridization), and compare these results with immunohistochemical demonstration of bcl-1 protein expression. VI. Determine the proliferative rate of MCL by immunohistochemistry and DNA content flow cytometry. V. Summarize the toxic effects associated with this treatment.