Imatinib Mesylate in Treating Patients With Locally Advanced or Metastatic Dermatofibrosarcoma Protuberans or Giant Cell Fibroblastoma

DISEASE CHARACTERISTICS: Histologically confirmed dermatofibrosarcoma protuberans or giant cell fibroblastoma Locally advanced or metastatic disease Measurable disease Not amenable to surgery, radiotherapy, or combined modality therapy with curative intent Documented progressive disease within the past 3 months Previously irradiated lesions must show disease progression Tumor expressing COL1A1/PDGF-beta by fluorescence in situ hybridization Translocation t(17;22)(q22;q13) No prior chemotherapy OR previously treated with 1, and only 1, line of combination chemotherapy with ifosfamide and doxorubicin OR 2 lines of single-agent therapy OR relapsed within 6 months after adjuvant chemotherapy PATIENT CHARACTERISTICS: Age 18 and over Performance status WHO 0-2 Life expectancy Not specified Hematopoietic Absolute neutrophil count ≥ 2,000/mm^3 Platelet count ≥ 100,000/mm^3 Hemoglobin ≥ 9 mg/dL* NOTE: *Transfusion allowed Hepatic SGOT or SGPT ≤ 2.5 times upper limit of normal (ULN) (5 times ULN if hepatic metastases are present) Bilirubin ≤ 1.5 times ULN No uncontrolled hepatic disease Renal Creatinine ≤ 1.5 times ULN No uncontrolled renal disease Other Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception during and for 3 months after study participation HIV negative No uncontrolled diabetes No active or uncontrolled infection No concurrent severe or uncontrolled medical disease No medical, psychological, familial, sociological, or geographical condition that would preclude study participation, compliance, or giving informed consent No other malignancy within the past 5 years except adequately treated basal cell or squamous cell skin cancer, carcinoma in situ of the cervix, or adequately treated stage I or II cancer currently in complete remission PRIOR CONCURRENT THERAPY: Biologic therapy More than 28 days since prior biologic therapy No concurrent filgrastim (G-CSF) or sargramostim (GM-CSF) No concurrent anticancer biologic agents Chemotherapy See Disease Characteristics More than 28 days since prior chemotherapy No concurrent chemotherapy Endocrine therapy Not specified Radiotherapy See Disease Characteristics At least 6 months since prior radiotherapy No concurrent radiotherapy Concurrent palliative radiotherapy allowed provided radiotherapy will not be administered to a target lesion Surgery Not specified Other More than 28 days since prior investigational drugs No concurrent therapeutic anticoagulation therapy with warfarin Concurrent low-molecular weight heparin or mini-dose warfarin for prophylaxis of central venous catheter thrombosis allowed No other concurrent anticancer agents No other concurrent investigational drugs No other concurrent cytostatic agents No other concurrent tyrosine kinase inhibitors