A pathologic fracture of an intracortical chondroma masking as an osteoid osteoma.

ABSTRACT

The differential diagnosis of a tibial intracortical diaphyseal lesion includes osteoid osteoma, periosteal chondroma, nonossifying fibroma, osteofibrous dysplasia, and adamantinoma. While osteoid osteomas represent 5% of all primary bone tumors, little is understood about intracortical chondromas. Intracortical chondroma was first described in 1990 and 7 reported cases have since been published. This article presents the first reported case of a pathologic fracture of an intracortical lesion in a child that shared radiographic and clinical features similar to those of osteoid osteoma, but on histopathologic examination revealed an intracortical chondroma. Our patient exhibited radiographic features of a poorly circumscribed cortical bone sclerosis, a centralized radiolucent nidus on computed tomography, and a hot bone scan of a lesion <1 cm in size that was consistent with an osteoid osteoma. An excision of the bone lesion was performed. The histopathology of the lesion revealed nodules of benign hyaline cartilage in cortical bone, consistent with an intracortical chondroma. Demarcated by cortical bone with mature Haversian systems rather than periosteum or cancellous bone, intracortical chondroma differs from the other 2 chondroma variants, periosteal chondroma and enchondroma, by its relationship to the surrounding bone. Enchondromas are characteristically understood to be asymptomatic. Intracortical chondromas along with periosteal chondromas have been found to present as painful lesions. The similarities with osteoid osteoma and intracortical chondroma in our patient make it circumspect in regards to ablating lesions (ie, needle radiofrequency ablation) without acquiring a biopsy in pediatric patients that both clinically and radiographically are presumably an osteoid osteoma.