Clinical History
65-year-old male patient with gait instability and hypofunction came to the emergency department.
Imaging Findings
This case is a typical SFT, presenting as a well-circumscribed mass with lobular external surfaces. It shows as a solid extra-axial mass in the left posterior fossa.
On unenhanced computed tomography it is seen as a hyperattenuating mass with marked heterogeneous enhancement after contrast administration. On MR imaging, the lesions is hypointense on T1-weighted images and on T2-weighted images, SFTs is markedly hypointense due to collagenous stroma and fibrosis. SFTs show marked homogeneous enhancement after gadolinium administration.
Postsurgical images show a complete resection of the tumour, and the anatomopathological report shows a neoplastic proliferation, consisting of mesenchymal cells. An immunohistochemical study shows that neoplastic cells are positive for CD34 (intense and diffuse) and negative for PFGA, EMA and S100.
Discussion
Solitary fibrous tumour (SFT) is a mesenchymal-origin neoplasm that may be benign or malignant. SFT is a rare tumour that mostly occurs in the thoracic cavity, especially in visceral pleura. However, SFT has been reported to occur outside of the pleura, such as in pericardium, peritoneum, lung, liver, upper respiratory tract, mediastinum, thyroid and parotid glands. It has also been reported in the CNS, although intracranial SFTs are rare. When SFT appears in the CNS, the most frequent locations are in the meninges as dural-based neoplasms, and commonly involve the parasagittal region, tentorium, and cerebellopontine angle. [1] Meningeal SFTs have a tendency to arise in the posterior fossa and spine. [2] Although SFT is an uncommon neoplasm, it has been reported with increasing frequency in different anatomic sites, including the CNS. [3]
The location of SFT in the brain is infrequent due to paucity of true connective tissue elements within the CNS. Their histogenesis is still unknown. The possibilities are that they could have arisen from perivascular connective tissue, from the pia-arachnoid, or from dural fibrocytes located in the brain. [4] In the literature, they almost always arise from the extra-axial space with a meningeal origin, however, cases of intraventricular tumours have been described. [5]
SFTs typically affect patients with a mean age at presentation between 55 and 65 years and no sex predilection. [6]
Although both SFT and meningioma present as dural-based tumours, meningioma usually appears isointense to brain parenchyma on both T1 and T2WI, and appears markedly hyperintense on T1WI post-contrast. [3] SFT could show variable intensities on T2WI, but many of them presented on MRI with markedly hypointense signal on T2WI due to collagen stroma and fibrosis. [5]
Although some imaging findings are characteristic of SFTs, histologic and immunohistochemical studies are mandatory for confirmatory diagnosis. [6]
Histopathologically, the SFT may appear very similar to other spindle cell neoplasms, fibrous meningioma. Morphologic features are not sufficient for making a differential diagnosis with a meningeal mass. Immunohistochemical profile is essential; CD34, an antigen, shows a diffuse and strong positivity in the SFT and shows a positive reaction for vimentin, whereas EMA and S-100 are negative. Fibrous meningioma is usually positive for EMA and negative for CD34. [2]
The treatment of choice is complete resection, it should be followed up due to a possible recurrence. [1] There is no established standard systemic therapy for metastatic disease; different targeted therapies, tyrosine kinase inhibitors and antiangiogenic agents, have shown therapeutic efficacy in patients with advanced SFTs. [6]
Differential Diagnosis List
Cerebral solitary fibrous tumour
Fibrous meningioma
Haemangiopericytoma
Final Diagnosis
Cerebral solitary fibrous tumour
