DISEASE CHARACTERISTICS:

• Diagnosis of one of the following:

  • Neurofibromatosis type 1 (NF1)

  • Progressive plexiform neurofibromas

    • Neurofibromas that have grown along the length of a nerve and may involve multiple fascicles and branches (spinal neurofibromas involve 2 or more levels with connection between the levels or extending laterally along the nerve)

    • Potential to cause significant morbidity such as:

      • Head and neck lesions that could compromise airway or great vessels
      • Brachial or lumbar plexus lesions that could cause nerve compression and loss of function
      • Lesions that could result in major deformity (e.g., orbital lesions)
      • Lesions of the limb that cause limb hypertrophy or loss of function
      • Painful lesions

• Meets at least 1 other diagnostic criteria for NF1

  • 6 or more cafe-au-lait spots (at least 0.5 cm in prepubertal patients or at least 1.5 cm in postpubertal patients)
  • Freckling in the axilla or groin
  • Optic glioma
  • 2 or more Lisch nodules
  • Distinctive bony lesion (dysplasia of the sphenoid bone or dysplasia or thinning of long bone cortex)
  • First-degree relative with NF1

• Measurable plexiform neurofibromas

  • At least 3 cm in one dimension
• Evidence of recurrent or progressive disease as documented by an increase in size or the presence of new plexiform neurofibromas on MRI
• No evidence of an optic glioma, malignant glioma, malignant peripheral nerve sheath tumor, or other cancer requiring chemotherapy or radiotherapy
• Prior surgery for progressive plexiform neurofibroma allowed provided neurofibroma was incompletely resected and is measurable
• Complete tumor resection not feasible or patient refused surgery

PATIENT CHARACTERISTICS:

Age:

• 3 to 25

Performance status:

• ECOG 0-2

Life expectancy:

• At least 12 months

Hematopoietic:

• Absolute granulocyte count at least 1,500/mm^3
• Hemoglobin at least 9.0 g/dL
• Platelet count at least 150,000/mm^3
• Fibrinogen normal

Hepatic:

• Bilirubin normal unless due to Gilbert's syndrome
• SGPT no greater than 2 times upper limit of normal
• No significant hepatic dysfunction

Renal:

• Creatinine normal for age OR
• Creatinine clearance at least 70 mL/min

Cardiovascular:

• No significant cardiac dysfunction

Pulmonary:

• No significant pulmonary dysfunction

Other:

• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception
• No clinically significant unrelated systemic illness that would preclude study participation
• No serious infections
• No significant organ dysfunction
• No metal implanted prostheses (e.g., vascular clamps or pacemakers) that would contraindicate an MRI

PRIOR CONCURRENT THERAPY:

Biologic therapy:

• At least 1 week since prior filgrastim (G-CSF)
• No concurrent anticancer immunotherapy

Chemotherapy:

• See Disease Characteristics
• No more than 1 prior myelosuppressive chemotherapy regimen
• At least 4 weeks since prior chemotherapy and recovered
• No concurrent anticancer chemotherapy

Endocrine therapy:

• No concurrent anticancer hormonal therapy

Radiotherapy:

• See Disease Characteristics
• At least 6 weeks since prior radiotherapy and recovered
• No concurrent anticancer radiotherapy

Surgery:

• See Disease Characteristics

Other:

• No prior tipifarnib
• At least 30 days since prior investigational agents
• No concurrent proton pump inhibitors (e.g., omeprazole, lansoprazole, pantoprazole, rabeprazole, or esomeprazole)
• No other concurrent investigational anticancer agents