Grade III solitary fibrous tumor/hemangiopericytoma: An enthralling intracranial tumor-A case report and literature review.

Hemangiopericytomas account for less than 1% of all intracranial tumors. In 2016, World Health Organization (WHO) unified the two terms into a single medical condition known as solitary fibrous tumor/hemangiopericytoma (SFT/HPC). Our patient is an 80-year-old woman with a past medical history of sick sinus syndrome status post pacemaker placement. She presented to the emergency department with progressive headaches for one month duration. Her headaches worsened at night, waking her up from sleep. They also increased in intensity by bending forward. Review of systems was significant for bilateral lower extremity weakness accompanied by difficulty walking. The motor exam was remarkable for right upper and right lower extremity 3/5 weakness. The gait was ataxic. A Computed tomography scan of the head without contrast revealed a large dural-based right parietal hyperdense mass with surrounding edema, mass effect, and compression of the right lateral ventricle atrium. A right-to-left midline shift was also noted. Given the fact that our patient had a pacemaker, she was not a candidate for a brain MRI. Neurosurgery successfully resected the mass. Histopathological studies confirmed WHO grade III anaplastic solitary fibrous tumor/hemangiopericytoma. The patient was discharged on adjuvant radiation with imaging surveillance given the grade and the extent of resection. This case highlights a rare type of intracranial mass that resembles meningioma on imaging studies. It also illustrates that solitary fibrous tumor/hemangiopericytoma should be kept as a differential diagnosis for brain masses, given its aggressive nature, and its potential of metastasis and recurrence.

Introduction

Hemangiopericytomas account for less than 1% of all intracranial tumors. Previously classified as capillary angioblastic meningiomas, these tumors possess similar genetic alterations to other solitary fibrous tumors of the dura involving the neuraxis [1,2]. Consequently, in 2016 the World Health Organization (WHO) unified the 2 terms into a single medical condition known as solitary fibrous tumor/hemangiopericytoma (SFT/HPC) [3]. We present a case of a SFT/HPC presenting in an elderly female with symptoms of intracranial mass effect.

Case presentation

Our patient is an 80-year-old woman with a past medical history of nicotine use disorder and sick sinus syndrome status post pacemaker placement. She presented to the emergency department with progressive, constant, tension-like headaches that had started one month prior. Her headaches worsened at night, waking her up from sleep. They also increased in intensity by bending forward. The patient did not report any alleviating factors or previous similar episodes. Review of systems was significant for bilateral lower extremity weakness accompanied by difficulty walking, eventually unable to stand due to fear of falling. Otherwise, the review of the systems was negative for seizures, sensory loss, aphasia, blurry vision, nausea, or vomiting. Physical examination showed stable vital signs. The motor exam was remarkable for right upper and right lower extremity 3/5 weakness. The gait was ataxic. Moreover, she had unremarkable cranial nerves and sensory exam. A computed tomography (CT) scan of the head without contrast revealed a large dural-based right parietal hyperdense mass with surrounding edema, mass effect, and compression of the right lateral ventricle's atrium. A right-to-left midline shift was also noted in Fig. 1, Fig. 2, Fig. 3. Given the fact that our patient had a pacemaker, she was not a candidate for a brain MRI. Intravenous dexamethasone was promptly given while neurosurgery successfully resected the mass. Histopathological studies revealed ten mitoses per ten high-power fields on microscopy, confirming WHO grade III anaplastic SFT/HPC. The patient was discharged on adjuvant radiation therapy with imaging surveillance given the grade and extent of resection.

Fig. 1

Computed tomography (CT) scan of the brain in axial view revealing a dural-based right parietal hyperdense mass with surrounding edema, mass effect, compression of the right lateral ventricle's atrium and a right-to-left midline shift.

Fig. 2

Computed tomography (CT) scan of the brain in sagittal view revealing a dural-based right parietal hyperdense mass with surrounding edema, mass effect and compression of the right lateral ventricle's atrium.

Fig. 3

Computed tomography (CT) scan of the brain in coronal view revealing a dural-based right parietal hyperdense mass with surrounding edema, compression of the right lateral ventricle's atrium and a right-to-left midline shift.

Discussion

Solitary fibrous tumors (SFTs) are a heterogeneous category of uncommon spindle cell neoplasms that typically arise from the pleura and peritoneum. They account for less than 2% of all soft tissue masses [4]. Hemangiopericytomas are highly cellular and mitotically active tumor that is abundant in pericellular reticulin. Unfortunately, these characteristics are associated with high recurrence and metastasis [5]. Carneiro et al. described the first case of SFT/HPC discovered in the meninges in 1996 and established histological characteristics for the differentiation from meningiomas [6]. Interestingly, recent studies revealed that these lesions share a common genetic, pathological, and immunohistochemistry alteration with solitary fibrous tumors of the dura, involving the neuraxis: 12q13 inversions and amplification of the NAB2-STAT6 reporter gene [2]. The World Health Organization (WHO) integrated the 2 terms in 2016 into a single medical condition known as solitary fibrous tumor/hemangiopericytoma (SFT/HPC) and categorized them into 3 grades (Table 1) [3].

Table 1

WHO 2016 solitary fibrous tumor/hemangiopericytoma (SFT/HPC) grades.

WHO grade (2016) [3]	Description	Phenotype	Behavior	Prior name
I	Spindle cell lesion with high collagen content and high cellularity.	SFT	Benign tumor	SFT
II	Less collagen content, more cellularity with “staghorn” vasculature.	SFT	Malignant tumor	HPC
III	Five or more mitoses per 10 high-power fields.	HPC	Malignant tumor	Anaplastic HPC

M. Fargen et al. reviewed the cases between 1996 and 2010, and they found that males and females are equally affected. Moreover, the tumors typically occur throughout the fifth decade [7]. The signs and symptoms are primarily connected to the tumor's location and size; headaches, focal neurological impairments, increased intracranial pressure, and seizures are the most common clinical manifestations [8].

SFT/HPC tumors frequently exhibit imaging characteristics similar to meningiomas. They are also difficult to differentiate histologically and are commonly misdiagnosed preoperatively, even though meningiomas are significantly more common and less likely to recur or spread extracranially [9,10]. Upon literature review, we collected the similarities and differences between the 2 entities and summarized them based on histological and radiological findings (Table 2).

Table 2

Literature review of the similarities and differences between FT/HPC and meningioma based on histological and radiological findings.

Features	SFT/HPC	Meningioma
Histopathology [9,10]	STAT6Sensitivity (96%)Specificity (100%)ALDH1 and CD34Sensitivity (84%)Specificity (97%)	SSTR2ASensitivity (95.2%)Specificity (92%)EMASensitivity (89.3%)Specificity (85%)
Imaging characteristics[11], [12], [13]	T1W1: IsointensityT2W1: IsointensityEnhancement pattern: UniformizingDural tail sign: absentIntratumoral calcification: absentEdge of tumor: multilobularAdjacent bone: eroded	T1W1: IsointensityT2W1: IsointensityEnhancement pattern: UniformizingDural tail sign: presentIntratumoral calcification: presentEdge of tumor: well definedAdjacent bone: thickened

Surgery is the gold standard of therapy. Complete excision of the tumor is preferable, as inadequate resection can result in the tumor reappearing or remaining cells continuing to proliferate [14]. Our patient pursued surgery and radiation therapy as a personal preference, considering her overall performance status. SFT/HPC has a noticeably high metastatic rate, ranging from 23% to 76%. Additionally, its clinical course is exceedingly aggressive, with recurrence rates ranging from 61% to 76% [15].

Conclusion

This case highlights a rare type of intracranial mass that resembles meningioma on imaging studies. It also illustrates that solitary fibrous tumor/hemangiopericytoma should be kept as a differential diagnosis for brain masses, given its aggressive nature, and its potential for metastasis and recurrence. Early detection and resection can ensure a favorable outcome in the proper clinical setting.