Imatinib Mesylate in Treating Patients With Recurrent or Refractory Fibromatosis

DISEASE CHARACTERISTICS: * Histologically confirmed aggressive fibromatosis (desmoid tumor) * Relapse or disease progression despite surgery, chemotherapy, radiotherapy, or any other treatment * Tumors must meet the following criteria: * Ineligible for complete surgical resection by carcinological exeresis OR surgery would cause severe mutilation * Cannot be treated with curative radiotherapy * Measurable disease by RECIST criteria * No prior malignancy PATIENT CHARACTERISTICS: * Not pregnant or nursing * Fertile patients must use effective contraception during and for 6 months after completion of study treatment * Absolute neutrophil count \> 1,000/mm\^3 * Platelet count \> 100,000/mm\^3 * Bilirubin \< 1.5 times upper limit of normal (ULN) * SGOT and SGPT \< 2.5 times ULN * Creatinine ≤ 2.5 times normal * No severe liver failure * No chronic somatic or psychiatric illness that would preclude study compliance * No known hypersensitivity to imatinib mesylate or one of its components * No geographical, social, or psychological reason that would inhibit follow-up PRIOR CONCURRENT THERAPY: * See Disease Characteristics * No concurrent immunomodulators\* * No concurrent hormonal treatments\* if used for fibromatosis * No concurrent cytotoxic drugs\* * No concurrent nonsteroidal anti-inflammatory drug\* if used for fibromatosis * Allowed if used as an analgesic 3 months prior to disease progression * No concurrent participation in another therapeutic investigational trial NOTE: \*If disease progression has occurred during this treatment, then the treatment must have ended ≥ 1 month prior to study entry