Solitary osteochondroma: spontaneous regression.

A 15-year-old female had been followed in our department of pediatric radiology since the age of 11, in order to control a solitary osteochondroma (exostosis) of the right distal femur. Radiographs of the right distal femur (face-profile) and high frequency ultrasound studies (12-5 MHz) of this area were performed to assess the size of the lesion and the thickness of the cartilaginous cap. Follow up of the lesion showed an increase in size from the age of 11 to the age of 12 with a a cartilaginous cap thickness of 3 mm. Coincident with a growth plate closure a thinning of the cartilaginous cap was documented by ultrasounds, reducing from 3 mm to < 1 mm at the age of 13 (Fig. C. Cartilaginous cap of the osteochondroma at the age of 12 C1 and 15 years C2). A spontaneous regression of the osteochondroma occurred in the following years ranging from the age of 13 (Fig. A) to the age of 15 (Fig. B).