Avulsion fracture of the anterior inferior iliac spine with abundant reactive ossification in the soft tissue.

Patients who have sustained an avulsion fracture and present clinically during the healing phase of the injury may manifest a mass that clinically and radiographically mimics a malignant neoplasm. A 15-year-old male soccer goalkeeper presented with a large ossified mass in the soft tissues overlying the right hip 6 months after experiencing a popping sensation in his hip joint during a game. Although an osteosarcoma was suspected clinically and radiographically, a Tru-Cut needle biopsy of the lesion revealed reactive bone formation. Correlation of the clinical, radiographic, and pathologic findings indicated an avulsion fracture of the anterior inferior iliac spine with abundant reactive ossification in the soft tissues. The healing phase of an avulsion fracture may clinically and radiographically be mistaken for neoplasia. In such cases, a Tru-Cut needle biopsy may reveal the reactive nature of the process.