Aggressive fibromatosis (AF, also known as desmoid tumor) is a fibroproliferative neoplasm that typically arises in the abdomen but can develop at other anatomic sites, most commonly in the extremities. These tumors have a relatively high local failure rate after primary treatment using surgery and/or radiotherapy, and although rarely giving rise to distant metastases, can be multifocal and, therefore, not surgically resectable. Moreover, tumor may recur adjacent to the site of surgical resection, underscoring the limitations of surgery in the palliative setting. Therefore, effective medical therapies for AF are needed to maintain quality of life and prolong survival.The goal of the current study was to better define the activity of imatinib in the treatment of AF and to determine the molecular basis for response/nonresponse

Inclusion Criteria:

1. Written consent;
2. Age ≥ 10 years;
3. Eastern Cooperative Oncology Group Performance status ≤ 2;
4. Histologically confirmed desmoid tumor;
5. Disease progression after local treatment
6. Measurable target lesion (RECIST criteria) ;
7. Adequate hematological, renal and liver functions :

Exclusion Criteria:

1. Other co-existing malignancies or malignancies diagnosed within the last 5 years with the exception of basal cell carcinoma or cervical cancer in situ.
2. Pregnant or lactating female
3. Evidence of any other significant clinical disorder or laboratory finding that makes it undesirable for the patient to participate in the study