Pathologic Fracture: A Rare Situation In Children. Pilotto C, Robazza M, Vergine M, Passone E. Clinica Pediatrica, Azienda Ospedaliero Universitaria Santa Maria Della Misericordia, Udine. RX tibia dx RMN T1Fs sag Introduction Pathological fracture is a rare condition in the paediatric patient. It should be suspected if the fracture involves an unusual district or if it is associated with minimal trauma. Case report An 11 years-old girl presented a spiroid fracture of the tibia, after an ankle sprain occurred during low-intensity sport activity. Leg X-ray showed a 5 cm multi-loculated radiolucent area surrounded by a thin corticalization layer associated with the fracture. A conservative treatment was initially chosenwithclosed reduction of the fracture and immobilization. An MRI showed a lesion with an hypointense signal on T1-weigthed sequences and a dishomogenous hyperintense signal onT2-weigthed images, with typical marrow oedema surrounded by haemorrage secondary to the fracture. The imaging was consistent with non-ossifying fibroma. As the child suffered from a consolidation delay, after 3 months she was treated with curettage and bone grafting. Discussion The non-ossifying fibroma (NOF)is the most common benign bone lesion in children. It is estimated between 30% and 40% of people <20 years of age. Usually it is asymptomatic and can be monitored without intervention. NOF should be treated only if it interferes with the bone healing process. ONSP XI Congresso Nazionale Pavia