[Radiological diagnosis of enchondroma protuberans of the humerus]

Enchondroma protuberans (EP) is an uncommon exophytic cartilaginous tumor described as an intramedullary osseous lesion that protrudes through a cortical defect in one of the sides of the affected bone and expands to the adjacent soft tissues. Due to its peculiar features on imaging studies, the main differential diagnosis is with osteochondroma, chondrosarcoma, and periosteal chondral tumors. In this article, we describe the imaging findings in two patients with EP in the humerus. We review the literature and discuss the imaging features that can enable a definitive diagnosis. The identification of the connection between the two components of the lesion through a cortical defect is a key finding for the diagnosis. Available imaging techniques, especially MRI, make it possible to establish the diagnosis in this type of lesions and thus to choose the appropriate treatment, reducing the chance of local recurrence and malignant transformation.