Primary Intracranial Solitary Fibrous Tumor
Intracranial solitary fibrous tumors (ISFTs) are rare mesenchymal neoplasms originating in the meninges and constitute a heterogeneous group of rare spindle-cell tumors that include benign and malignant neoplasms of which hemangiopericytoma is nowadays considered a cellular phenotypic variant. ISFT usually shows benign or indolent clinical behavior 1).
Primary Intracranial Solitary Fibrous Tumor (SFT) involving the central nervous system (CNS) was first reported in 1996 by Carneiro et al, who described 7 cases of meningeal SFT that could be distinguished from fibrous meningioma on morphologic and immunohistochemical grounds 2).
For its rarity and resemblance to other more common brain tumors, such as meningioma and hemangiopericytomas, intracranial SFT (ISFT) is often poorly recognized and remains a diagnostic challenge.
Although there are no pathognomonic imaging findings, some imaging features, such as the “black-and-white mixed” pattern on T2-weighted images and marked heterogeneous enhancement, might be helpful in the diagnosis of intracranial solitary fibrous tumor
A 62-year-old man with headache and memory disturbance for 2 years. A, Noncontrast CT shows a heterogenous hyperattenuated multilobulated tumor in left middle cranial fossa. B, Contrast-enhanced CT, intense but inhomogeneous contrast enhancement is noted. C, T1-weighted axial MR image, a large lobulated mass is seen in the left paraclinoid portion to the tentorium. D, T2-weighted axial MR image reveals 2 different signal intensity portions of the mass, hyposignal intensity and hypersignal intensity to gray matter. E and F, Gadolinium-enhanced T1-weighted axial and coronal MR images show marked and heterogenous enhancement. The tumor is partially implanted on the surface of the tentorium (arrows). Memory disturbance might be because of the mass effect on the limbic system. G, Selective injection of the left internal carotid artery (capillary phase); the tumor is supplied at its periphery by pial branches. H, Selective injection of the left external carotid artery; there is tumor blushing with dysplastic dilation of the tumor vessels. There is no demonstrable significant arteriovenous shunt or early venous drainage. 3).
Yamaguchi et al. reported a very rare case of intracranial SFT in a 55-year-old woman who presented with gait disturbance and numbness in bilateral upper limbs from three months prior to visiting the hospital. Head MRI revealed a homogeneously enhancing mass lesion located primarily in the fourth ventricle extending into the spinal canal and left foramen of Luschka, with a maximum diameter of 60 mm. Notably, this tumor presented spontaneous partial regression during waiting planned surgery without therapy, including chemotherapy and radiotherapy. This patient underwent a midline suboccipital craniotomy and resection of the tumor. Interestingly, there was no attachment to the dura mater of the posterior cranial fossa and the lesion was only attached to the dorsal part of the medulla oblongata.
Although the location of the SFT in the fourth ventricle is rare, SFT should be considered as one of the differential diagnosis of fourth ventricle tumors. In addition, this case indicates that SFT in the fourth ventricle may regress on occasion spontaneously without a precisely known cause for this spontaneous partial regression 4).
Torazawa et al., encountered a case of small solitary fibrous tumor in the optic canal causing rapid visual deterioration. The radiographic findings of pre-operative imaging studies were compatible with those of meningioma; however, unlike meningioma, bleeding from the tumor was very profuse during the operation. The endoscopic transnasal approach was effective for handling the highly vascularized tumor in this delicate region, and gross total removal was achieved with postoperative gradual improvement in his visual function. Nevertheless, the tumor recurred after six months, and re-resection was performed with using the same surgical corridor, followed by adjuvant radiotherapy.
Endoscopic transnasal surgery is a valuable option for aggressive lesions in the optic canal. Although the efficacy of radiotherapy for SFT remains controversial, it should be considered when the tumor shows progressive features 5).
A 63-year-old female patient who had confused mentality, without other neurological deficit. The brain MRI showed an ovoid mass in the right frontal lobe. The tumor was surgically removed grossly and totally, and the pathologic diagnosis was SFT. At 55 months after the surgery, the tumor recurred at the primary site and at an adjacent area. A second operation was thus done, and the tumor was again surgically removed grossly and totally. The pathologic diagnosis was the same as the previous, but the Ki-67 index was elevated. Ten months later, two small recurring tumors in the right frontal skull base were found in the follow-up MRI. It was decided that radiation therapy be done, and MRI was done again 3 months later. In the follow-up MRI, the size of the recurring mass was found to have decreased, and the patient did not manifest any significant symptom. Follow-up will again be done 18 months after the second surgery 6).