RATIONALE: Drugs used in chemotherapy use different ways to stop tumor cells from dividing so they stop growing or die.

PURPOSE: Phase I trial to study the effectiveness of melphalan in patients with persistent or recurrent neoplastic meningitis.

OBJECTIVES: I. Determine the maximum tolerated dose of intrathecal melphalan (L-PAM) in patients with neoplastic meningitis. II. Determine the CSF and serum pharmacokinetics of L-PAM administered via an Ommaya reservoir to these patients.

OUTLINE: This is a dose escalation study. Patients receive melphalan (L-PAM) intrathecally (IT) via lumbar puncture or Ommaya reservoir twice a week for 2 weeks. Cohorts of 3-6 patients receive escalating doses of melphalan until the maximum tolerated dose (MTD) is determined. The MTD is defined as the dose preceding that at which 4 of 6 patients experience dose-limiting toxicity. At least 3 patients receive L-PAM via Ommaya reservoir at the MTD. Patients with objective or significant clinical response may receive additional L-PAM IT once a week for 2 consecutive weeks, every other week for 2 doses, and then monthly thereafter. Patients are followed every 12 weeks for 1 year or until disease progression.

PROJECTED ACCRUAL: A minimum of 3 children and 3 adults per dose level will be accrued for this study.

DISEASE CHARACTERISTICS: Histologically confirmed malignancy that is metastatic to the CSF or leptomeningeal/subarachnoid space, including the following: Leukemia Lymphoma Germ cell tumors Persistent or recurrent disease required Cytologic evidence of malignancy in CSF or evidence of leptomeningeal tumor by CT or MRI No obstructive hydrocephalus or complete block of spinal CSF pathways on pre- study MRI or CT No rapidly progressing or deteriorating neurological deficit

PATIENT CHARACTERISTICS: Age: 3 and over Performance status: Karnofsky 60-100% (age 10 and over) OR Lansky 60-100% (age under 10) Life expectancy: At least 8 weeks Hematopoietic: Absolute neutrophil count greater than 1,000/mm3* Platelet count greater than 100,000/mm3* * Lower values allowed with approval of the investigator Hepatic: Bilirubin less than 3.0 mg/dL Renal: Creatinine less than 2 mg/dL Blood urea nitrogen less than 30 mg/dL Electrolytes (including calcium, magnesium, phosphate) normal Other: No active infection Negative pregnancy test Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: Prior systemic chemotherapy within 3 weeks of entry allowed at investigator's discretion At least 3 weeks since prior intrathecal chemotherapy No other concurrent intrathecal chemotherapy Endocrine therapy: Not specified Radiotherapy: At least 3 weeks since prior radiotherapy to the CNS No concurrent radiotherapy to the CNS Surgery: Not specified