Intracranial chondroma is a rare benign tumor with an incidence of 0.2-0.3% of all the intracranial tumors (4, 5). They mostly originate from the skull base or bulges into the cranial cavity from nasal sinuses (1). However, approximately 15-30% of intracranial chondromas do not arise from the base of the skull but rather are intradural. They can arise in the ventricles, choroid plexus or at convexity in contact with the dura mater or the falx (5). In extremely rare instances, intracranial chondromas are located within the brain parenchyma and seem to have no attachment to the dura mater or falx cerebri (5). Intracranial chondroma originating from falx is a rare neoplasm with no more than 30 reported cases available (1). Intracerebral chondromas are classified as soft tissue chondroma in contrast with bone chondromas (chondrogenic tumor). Histopathogenis of this type of tumor is not well-known. Some authors suggested that the tumor may originate from meningeal fibroblasts metaplasia, others suggested that the tumor may arise from multipotential or perivascular mesenchymal cells or aberrant nests of cartilage forming cells in the dura mater. Traumatic displacement of cartilage is another theory proposed in accordance to existing cases of head trauma presenting with chondroma at the trauma site (1, 2, 4).
They usually occur in young adults with a peak incidence in the third decade. The age of patients reported in the literature ranges from 15 months to 60 years. There is no sex predominance (2,4).
Intracranial chondromas are slow-growing tumors that are usually large at presentation (1,2). Clinical manifestations of the tumor are not specific and depend on tumor location. On CT scan, intracranial chondromas appear as a mass of variable densities due to the extent of calcifications, with minimal to moderate rim contrast enhancement. MRI shows a well circumscribed lesion of intermediate to low intensity on T1 weighted images, and mixed intensity on T2 weighted images. Chondromas are well-demarcated tumors and do not invade surrounding structures (5). In this case, the dural tail of the lesion on tentorium suggested an extra axial lesion, inserted on dura. An elevated N-Acetylaspartate peak (2.04 ppm) was observed on MR spectroscopy. This peak is usually considered as a neuronal marker. Thus it does not seem to fit with an extra axial tumor. Indeed, it most probably reflects elevated specific metabolites within the tumor, such as proteoglycans (2.04 ppm), and, if recognized, could have suggested the diagnosis pre operatively (3).
Histological examination reveals a tumor composed of lobulated sheets of mature hyaline cartilage without any evidence of atypia. The most common differential diagnoses are chondrosarcomas that are distinct by the presence of atypia and many mitotic figures (4). Chondromas may also mimic meningiomas or solitary fibrous tumors, but histological aspects are very different.
The prognosis of intracranial chondroma is generally good. Complete surgical removal remains the treatment of choice (2, 4, 5).
Contributed by Aurélie Beaufrère, Mathilde Fouet, Onorina Bruno, Dominique Cazals-Hatem, Stéphane Goutagny