Introduction enchondromas rarely exceed 3–6 cm in long bones. Although the risk of developing secondary chondrosarcoma has been reported up to 4% in solitary lesions, it is not known if size represents a risk factor for transformation. Objective to describe three exceptional cases of enchondromas of the entire femur whereof one dedifferentiated in chondrosarcoma. Results two patients present stable disease at 5 and 6 years of follow-up; the third, already diagnosed with a dedifferentiated chondrosarcoma, died 14 months after the index surgery for systemic disease. Conclusion based on these observations, our hypothesis is that lesion size is an important risk factor for malignant transformation.
