Chondroma is a benign tumor of mature hyaline cartilage and is infrequently encountered in the head and neck region. Intracranial chondromas comprise 0.2%–0.5% of all intracerebral tumors [1]. Intracranially, they are predominantly found in the skull base, originating from the rests of embryonic cartilage along the sphenopetrosal and sphenooccipital synchondroses [2]. Less commonly, they can arise from falx, convexity dura, ventricular ependyma, or brain parenchyma [34]. The radiological appearance of these tumors is deceiving and requires histopathological confirmation for diagnosis.

A 53-year-old female patient, known hypertensive, presented to us with a history of episodic holocranial headaches accompanied with vomiting. Her neurological examination did not reveal any neurological deficits. CT brain plain scan showed a well-defined extra-axial lesion measuring approximately 6×2.2×4.4 cm in the left frontal para-sagittal convexity region with peripheral specks of calcification and hyperostosis of the overlying bone. The lesion was causing effacement of the left frontal lobe. MRI revealed a T1 weighted isointense, T2 weighted and FLAIR hypointense lesion, showing peripheral rim and central foci of enhancement on post-contrast scan. The lesion did not show diffusion restriction and was hypoperfused, as confirmed by the arterial spin labeling MRI perfusion sequence. It was abutting the superior sagittal sinus (Fig. 1A-C). A working diagnosis of a meningioma or a solitary fibrous tumor was made.

She was subjected to left frontal para-sagittal craniotomy. Intra-operatively, a well-demarcated, pearly-white, firm mass originating from the falx was revealed. The falcine attachment was identified and meticulously dissected, protecting the superior sagittal sinus, and an en-masse resection of the lesion was carried out. The overlying dura was excised, and dural closure was achieved using the pericranial graft. The postoperative MRI revealed complete tumor excision without any insults or injury to the superior sagittal sinus (Figs. 1D-F and 2).

Histopathological examination revealed a well-circumscribed cartilaginous tumor showing mature chondrocytes in the lacunae. The background showed chondroid material interspersed with areas of hyalinised to myxoid stroma surrounding blood vessels. There were no features of atypia or binucleation. Mitosis was inconspicuous. Immunohistochemistry was performed. S100 highlighted the chondrocytes. Somatostatin receptor 2a (SSTR2A) and epithelial membrane antigen (EMA) were negative in the cells in the lacunae, ruling out meningothelial origin (chondroid meningioma). The mindbomb homolog-1 (MIB-1) labelling index was low, indicating a low proliferative rate. Overall features were consistent with a chondroma (Fig. 3).

The patient’s convalescence was uneventful, and she was discharged on postoperative day 3 without any neurological deficit. No adjuvant treatment was provided during the postoperative period. The patient remains well, with no residual or recurrent lesions, after a 13-month follow-up.

Chondroma is a benign cartilage tumor that is rarely encountered intracranially. It comprises of 0.2%–0.5% of all intracranial neoplasms [1]. Among the intracranial locations, it is commonly encountered at the skull base, arising from the sphenopetrosal and sphenooccipital synchondroses [2]. It can rarely be encountered arising from the convexity meninges and dural folds like falx. It has also been reported to originate from the ependymal lining [34]. It exhibits no sex preponderance or any age distribution [5]. Intracranial chondroma, though usually encountered as an isolated mass, has also shown an association with systemic chondromatosis conditions, such as Mafucci’s syndrome and Ollier’s disease [6].

Intracerebral chondroma is thought to result from the proliferation of the ectopic embryologic chondrocytes or the transformation of the perivascular mesenchymal tissue [7]. The ones arising from the meningeal or ependymal lining are believed to originate from the cartilaginous metaplasia of the fibroblasts [8]. Some authors also believe that they develop from the development of heterotopic chondrocytes [9]. Theories of these tumors forming from displaced cartilage caused by trauma or infection have also been published [10].

They can present with a gamut of clinical features predominantly governed by their anatomical location and lesion size. Their slow-growing nature explains their clinically dormant nature until they reach a significant size. They can present with symptoms as benign as occasional headache, which can be gradually progressive and debilitating, to more grave symptoms like seizures. Patients have also been reported to present with hemiparesis and visual disturbances [11]. A limited number of patients are reported to present with mania or personality changes [12].

Imaging characteristics are often misleading and are not pathognomonic. These lesions are encountered in the anterior cranial fossa, cavernous sinus, petrous apex, clivus, posterior fossa, frontal lobes, and para-falcine regions. On plain CT images, they usually appear as hyperdense lesion, although the density can vary. The lesion can also have some irregular calcifications. The adjacent bone can be hyperostotic or can even show some erosion. Post-contrast CT scans can show slight or no enhancement. On MR imaging, they are usually homogeneously isointense on T1W images and hypointense on T2W images, and they do not display contrast enhancement except for the occasional peripheral enhancement. They do not exhibit a dural tail, which helps to differentiate them from its close differential of meningioma along with the enhancement pattern, which is quite brilliant and homogenous in the latter [13]. Lacerte et al. [14] proposed the classification of these tumors into two distinct types. Type 1 tumors are more classic, uniformly isodense and homogenous on CT. Type 2 tumors appear hypodense in the central area.

Their management is fairly straightforward. Gross total resection of the tumor suffices, and no long-term recurrence has been encountered in patients in whom gross total resection is encountered. Caution should be exhibited while separating the tumors in the para-falcine from the adjacent sinus. In patients with partial resection, evident atypia and high mitotic activity, radiotherapy is recommended [15].

Histopathology review of the specimen plays a pivotal role in establishing the diagnosis. The classical presence of mature chondrocytes in a cartilaginous background prompts the diagnosis of chondroma. The cornerstone remains in excluding the differential diagnosis, especially given the rare location. The first step in diagnosing chondroma is to examine for any features of malignancy to rule out low-grade chondrosarcoma. The morphological features of distinction are infiltration, cellularity, bi/multinucleation, atypia, mitosis, and necrosis. Intracranial chondrosarcoma is predominantly skull base and low grade.

Given intracranial location, the other differentials with chondroid matrix that need to be considered are chondroid meningioma and chondroid chordoma [16]. These tumors have different cells of origin and differentiation, meningothelial cells and notochordal remnants. Thus, immunohistochemistry plays a role. SSTR2a, EMA, and cytokeratin brachyury are positive in meningiomas and chordomas, respectively. Only a handful of cases of these tumors arising from the falx have been reported, as described in Table 1[13171819202122232425].

In conclusion, this report highlights a rare intracranial location at which chondroma can be encountered. It also highlights that it is unlikely to diagnose this tumor based on its presentation and neuroimaging characteristics. Histopathology remains the gold standard for the diagnosis of these tumors. Complete resection of this tumor has an excellent prognosis and doesn’t warrant any adjuvant treatment.