DX-8951f in Treating Children With Advanced Solid Tumors or Lymphomas

DISEASE CHARACTERISTICS: * Histologically confirmed advanced solid tumors, including brain tumors and lymphomas, that have failed standard therapy (surgery, radiotherapy, endocrine therapy, or chemotherapy) or for which no standard therapy exists * Histology requirement waived for brain stem gliomas PATIENT CHARACTERISTICS: Age: * 21 and under at diagnosis Performance status: * ECOG 0-2 Life expectancy: * At least 8 weeks Hematopoietic: * Absolute neutrophil count at least 750/mm\^3 * Platelet count at least 75,000/mm\^3 * Hemoglobin at least 8.5 g/dL Hepatic: * Bilirubin no greater than 1.5 mg/dL * SGOT or SGPT no greater than 2.5 times upper limit of normal (ULN) (5 times ULN if liver metastases) Renal: * Creatinine no greater than 1.5 times ULN OR * GFR at least 70 mL/min Other: * Not pregnant or nursing * Negative pregnancy test * No history of severe or life-threatening hypersensitivity to camptothecin analogs * HIV negative * No other concurrent severe or uncontrolled medical illness * No systemic infection PRIOR CONCURRENT THERAPY: Biologic therapy: * Recovered from prior immunotherapy Chemotherapy: * See Disease Characteristics * Recovered from prior chemotherapy Endocrine therapy: * See Disease Characteristics Radiotherapy: * See Disease Characteristics * At least 4 weeks since prior extensive radiotherapy involving cranial, whole pelvic, or at least 25% of bone marrow reserve * Recovered from prior radiotherapy * Concurrent localized radi…