Extensive anterior skull-base mesenchymal chondrosarcoma: unusual cause of multiple indolent masses on the forehead

Primary intracranial occurrence of an extraskeletal mesenchymal chondrosarcoma (MC) is unusual. The commonly involved sites are the orbit, clivus and temporo-occipital junction. Occurrence of the lesion in the anterior skull-base (ASB) in an infiltrative manner and with extra-calvarial involvement, is anecdotal. We report the case of a 35-year-old woman who presented with two indolent swellings on the forehead for a duration of 1 year. Examination revealed impaired visual acuity and complete external ophthalmoplegia in the right eye and 5 × 6 cm and 2 × 3 cm sized hard masses on the forehead. CT and MRI revealed a large, intensely enhancing ASB mass with extensions into the right orbit, ethmoid sinus, nasal cavity, and anteriorly, into the subcutaneous tissue of the frontal scalp through erosions in the bone. At surgery via a right frontal recraniotomy, the lesion was found to be firm and very vascular. Owing to its extreme vascularity, decompression was limited to excision of the intracranial and extra-calvarial components of the lesion. Histopathology was consistent with the diagnosis of MC. The patient was advised a second stage surgery for excision of the residual lesion. She, however, opted for radiation therapy and was lost to follow-up. This report, with one of the most extensive ASB MCs described to date, adds to the list of rare differentials of indolent forehead masses in the diagnostic armamentarium of the neuropathologist.