Aggressive Fibromatosis with Bone Involvement- A Case Report

Aggressive fibromatosis is a condition marked by the presence of desmoids tumours, which are benign, slow-growing musculo-aponeurotic tumours with no evidence of any metastatic potential6. It is known to involve muscle, subcutaneous tissue and neurovascular structures. However, bone involvement is very rare1. We have presented the case report of a 13 year old boy with aggressive fibromatosis in the left gluteal region involving the supra acetabular portion of ilium and a part of ischium. Clinical examination revealed a firm swelling about 6x5x1 centimetres in the upper outer quadrant of left gluteal region. Complete blood count and ESR were normal. X-ray pelvis with both hips revealed an osteolytic lesion in the supra acetabular portion of left ilium. Computed Tomography showed geographic, lytic lesions involving the supra acetabular region of left ilium, quadrilateral plate and a part of ischium. MRI showed a soft tissue mass adjacent to the left ilium, infiltrating in to supra acetabular region of left ilium, and a part of ischium. With these findings our differential diagnoses were chronic osteomyelitis, eosinophlic granuloma and cystic type of fibrous dysplsia. CT scan guided FNAC showed degenerated osteocytes with occasional osteoclastic giant cells and inflammatory mononuclear cells. Then we did a wide local excision of the tumour with curettage of the surrounding bone. Histopathological examination of the specimen was suggestive of aggressive fibromatosis. Considering the hypercellularity and local aggressive behaviour of the tumour we diagnosed it as aggressive fibromatosis. In our two years of follow up the patient did not show any signs of recurrence. This case is being reported for its rarity since fibromatosis involving the bone is an unusual event.