Malignant Transformation of an Osteochondroma into a Chondrosarcoma in the Skull Base: A Rare Case Report

Abstract

Osteochondromas are benign tumors of skeletal bones that are not commonly seen in the skull. Primary chondrosarcomas of the skull base, on the other hand, are more frequently seen and tend to arise from the sphenoethmoidal regions and petroclival synchondrosis. Chondrosarcoma can also develop secondarily from malignant transformation. However, only one other known reported case of malignant transformation of an osteochondroma into a chondrosarcoma of the skull base has been described in the literature. We present the case of a 29 year old male who presented with right periorbital pain and was found to have an extra-axial lobulated skull base mass with classical features of chondrosarcoma; which ended up being concordant with pathology. However, the petroclival synchondrosis was found to remain intact and not involving the lesion, thus precluding a primary chondrosarcoma that would typically arise from the synchondrosis. Instead, an  osseous protrusion arising off the body of the right sphenoid bone was found originating from the lesion, and thus felt to represent a malignant transformation of a primary osteochondroma of the skull base into a chondrosarcoma.