Pediatric aneurysmal bone cyst of the distal tibia.

A rare, large pediatric aneurysmal bone cyst with pathologic fracture of the distal tibia of a 4-year-old female was presented. Classic radiographic and magnetic resonance imaging findings have been discussed. In a comprehensive review of the literature, aneurysmal bone cysts are an infrequently reported neoplasm of the foot and ankle bones. Lesions are characteristically seen in patients younger than 20 years of age, but rarely younger than 5 years. The benign cyst has a 2:1 female-to male predilection. In long bones, the lesion is typically metaphyseal in nature. Although the pathogenesis is still unknown, there exists the possibility of two types of aneurysmal bone cysts: a primary type without preexisting lesion and a secondary form associated with some other lesion. The diagnosis of aneurysmal bone cyst can be strongly suspected by correlating the radiographic and magnetic resonance imaging findings. For definitive diagnosis, accurate histologic evaluation is imperative to rule out any confusion or possibility with a malignant tumor.