[Solitary infantile myofibromatosis of bone]

We report one case of Solitary infantile Myofibromatosis of Bone in a 14-year old girl. Radiologic features of the tibial lesion were consistent with the diagnosis of a benign bone tumor. The final diagnosis was made on a total resection of the tumor. Histologically, the tumor consisted of nodules, hyalinized or cellular, with spindle-shaped cells resembling fibroblasts or smooth-muscle cells. There were numerous vascular spaces in close contact with these nodules. The tumor cells were immunoreactive with anti-alpha-smooth muscle actin antibodies. These data were consistent with the diagnosis of Myofibromatosis. The histologic features were similar to those of Infantile Myofibromatosis of other sites such as skin and soft tissue. The case reported is rare and not yet published, due to the age and sex of the patient, and the location of the tumor.