OBJECTIVES:~Primary~Determine the therapeutic activity of imatinib mesylate in patients with locally advanced or metastatic dermatofibrosarcoma protuberans or giant cell fibroblastoma.~Determine the progression-free rate at 14 weeks in patients treated with this drug.~Secondary~Determine objective response rate, progression-free survival, and overall survival in patients treated with this drug.~Determine the duration of response in patients treated with this drug.~OUTLINE: This is an open-label, non-randomized, multicenter study.~Patients receive oral imatinib mesylate twice daily for at least 14 weeks in the absence of disease progression or unacceptable toxicity. Patients with stable disease after 14 weeks receive imatinib mesylate for 12 additional weeks. Patients with a partial or complete response at 14 weeks undergo surgical resection if possible. If surgical resection of all remaining tumor is not possible OR if complete resection is not achieved (section margins positive), patients continue to receive imatinib mesylate in the absence of disease progression~Patients are followed monthly for 6 months, every 3 months for 6 months, every 6 months for 2 years, and then annually thereafter.~PROJECTED ACCRUAL: A total of 44 patients will be accrued for this study within 2 years.
RATIONALE: Imatinib mesylate may stop the growth of tumor cells by blocking the enzymes necessary for their growth.~PURPOSE: This phase II trial is studying how well imatinib mesylate works in treating patients with locally advanced or metastatic dermatofibrosarcoma protuberans or giant cell fibroblastoma.