Inclusion Criteria:

- Patients with histological confirmed aggressive fibromatosis (desmoid tumor)

- Measurable disease according to the RECIST criteria

- Evidence of relapse or disease progression within the last 6 months (based on RECIST
criteria) in computed tomography or magnetic resonance imaging

- No possibility of complete surgical resection or cases in which surgical therapy
leaving a large tissue defect, functional deficit or disfigurement would be required

- No possibility of curative radiotherapy with acceptable toxicity and/or late
morbidity

- Previous treatment of the tumor region by surgical intervention and/or radiotherapy
and/or antihormonal therapy possible

- Age > or = 18 years

- WHO PS < or = 1

- Effective contraception during study medication

- Signed informed consent form

Exclusion Criteria:

- Surgical intervention < 4 weeks

- Prior therapy with imatinib

- Pregnancy or lactation

- Severe hepatic dysfunction

- Known allergic reaction to imatinib or one of its components

- The following laboratory values: Absolute neutrophil count < 1.5 x 103/mm3, Platelets
< 100,000/mm3, Serum creatinine > or = 2.5 mg/dl, SGOT and/or SGPT > 2.5 x ULN (upper
limit of normal), Total bilirubin > 1.5 x ULN

- Participation in another study (four weeks before and during the study)

- Prior malignancy apart from completely resected basal cell carcinoma of the skin or
carcinoma in situ of the uterine cervix