Aneurysmal bone cyst of the first metatarsal bone mimicking malignant tumor.

The clinical results of roentgenographic examination in an eight-year-old girl with a large tumor in the first metatarsus suggested malignancy. The definitive pathologic diagnosis was atypical aneurysmal bone cyst. Massive bone grafting and preservation of the surrounding joints were successful, and a functional foot was obtained two years after operation.