Intracranial mesenchymal chondrosarcoma

A 30-year-old female presented with right-sided headache, blurred vision, vertigo, and weakness in the left upper and lower limbs for twenty days. There was no history of fever, seizure or altered sensorium.

MRI scan of brain revealed a large extra-axial heterogeneous mass lesion with lobulated margins adherent to falx in the right parasagittal frontoparietal region. It measured 5.2 x 7.1 x 5.0cm (CC x AP X TR). The lesion was predominantly hypointense in T1W images and hyperintense in T2W images. SW images showed dense calcifications within the mass lesion. A peripheral pattern of diffusion restriction was seen in DW images. The mass showed heterogenous enhancement with contrast. Moderate surrounding edema was noted. The right lateral and third ventricles were compressed along with midline shift to left side. No other intracranial lesions were noted. Subsequently, right frontoparietal craniotomy and tumor excision were done and histopathological examination revealed a biphasic tumor composed of undifferentiated small round cells admixed with islands of hyaline cartilage consistent with mesenchymal chondrosarcoma. The cartilage component was more cellular with a greater degree of nuclear atypia and hyperchromasia.

Intracranial mesenchymal chondrosarcoma (IMC) is a rare malignant neoplastic lesion consisting of both undifferentiated mesenchymal cells and hyaline cartilage with an incidence of  0.2-0.7 cases per hundred thousand population [1]. Dahlin and Henderson were the first ones to report such a case [2]. Mesenchymal chondrosarcoma can be osseous involving the pelvis, ribs, femur, long bones, spine, and mandible, or extraosseous which can involve the soft tissues or central nervous system [3,4]. The skull base is the commonest site of intracranial chondrosarcoma [5]. Clinical symptoms occur due to raised intracranial pressure or due to compression of cranial nerves.

CT, MRI and histopathology are the modalities used for the diagnosis of intracranial mesenchymal chondrosarcoma. CT shows iso to hyper dense lesion with interspersed calcifications and heterogenous enhancement. MRI shows a T1 hypointense and T2 hyperintense mass with interspersed low signal intensity due to the presence of well-defined cartilage or calcifications. Post contrast images show heterogenous enhancement. Neurovascular invasion can be assessed by MRI [6]. Histology reveals biphasic features, including areas of well-differentiated cartilage and small undifferentiated mesenchymal cells. The cartilaginous component stains positively for S-100 protein and the undifferentiated mesenchymal component stains positively for vimentin [7].

Treatment comprises excision followed by adjuvant radiotherapy. This tumor has a high likelihood of local recurrence and surgery alone is not adequate [8]. Post-operatively, a  close follow-up should be performed for checking any tumor progression or recurrence.

Although IMC is very rare, the radiologist should be aware of this possibility when tumors with dural attachment occur in young adults.