OBJECTIVES: I. Compare the event free survival of children with advanced stage large cell lymphoma treated with modified APO (doxorubicin/prednisone/vincristine/mercaptopurine) with or without intermediate-dose methotrexate/high dose cytarabine as maintenance therapy following induction therapy with APO. II. Characterize further the immunophenotypic and morphologic correlates of pediatric large cell lymphoma.