Delayed cervical spine metastasis from intracranial solitary fibrous tumor

INTRODUCTION

A solitary fibrous tumor (SFT) is a hypervascular sarcomatous tumor arising most likely from Zimmermann pericytes around the osseous capillaries and venules. Central nervous system (CNS) origin accounts for <1% of all CNS tumors and 2.4% of all meningeal tumors.^[2] Intracranial SFTs involving the spine are rare with only a few reports of isolated cervical spine metastasis.^{[1,8,10,14-16]}

We report a case of intracranial SFT with isolated cervical spinal metastasis after a 2-year dormant period. There was no evidence of metastatic lesions elsewhere including no local intracranial recurrence despite regular clinical and radiological screening. The scarcity of literature makes it difficult for a consensus management and follow-up plan. This report emphasizes metastatic propensities, radiological features, and management strategies, underscoring long-term clinical surveillance.

CASE REPORT

A 35-year-old female presented with neck pain, radiating to the right shoulder with weakness of the upper limb for the last 10 days. Two years ago, she had surgical resection of the right temporal mass and the histopathology revealed SFT grade III (World Health Organization [WHO] classification 2021).^[7] Postoperatively, the patient received adjuvant radiotherapy (RT) and no recurrence on magnetic resonance imaging (MRI) brain after 2 years. On clinical examination, her distal muscle group had decreased power (grade 3/5) with impaired sensation in the right C7 and C8 dermatomes and exaggerated deep tendon reflexes. MRI cervical spine revealed decreased C7 vertebral height with mild retropulsion, with contrast enhancement, involving the right pedicle and encroaching bilateral exiting neural foramina, impinging on the nerve roots [Figure 1]. The positron emission tomography (PET) scan at 1 year was unremarkable for any metastatic disease.

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Figure 1:

(a) Computed tomography sagittal view of the cervical spine showing a collapsed C7 vertebral body with retropulsion and expansile C7 vertebral body lesion, replacing most of the vertebral body. (b) T1 post-contrast and (c) T2-weighted sagittal and (d) Axial magnetic resonance imaging. Decreased vertebral height of C7 vertebra with mild retropulsion and intense post-gadolinium enhancement of the vertebral body and right pedicle.

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The patient had a C7 corpectomy, with fusion using an expandable cage (ADDplus™, Ulrich Medical, Germany) and fixation by plating. The mass lesion was soft, grayish, and highly vascular. Histopathology revealed SFT grade 3 characterized by short fascicles of a monotonous population of ovoid cells with monomorphic nuclei, admixed with the background of variably sized and branched vasculature called staghorn appearance [Figure 2]. Postoperatively, the patient got immediate pain relief and received adjuvant RT of the spine along with neurorehabilitation.

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Figure 2:

(a) Light microscopic examination of the tumor showing clusters of tumor cells in a background of staghorn blood vessels (H&E×100). (b) High-power view of the tumor showing monomorphic ovoid nuclei with numerous mitotic figures (red arrows) (H&E×400). (c) Immunohistochemistry with antibody against STAT6 diffusely expressed in the nuclei (immunohistochemistry×400). (d) Light microscopic examination of the recurrent tumor in the cervical spine showing bony trabeculae (red arrows) surrounded by tumor cells (H&E×100).

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DISCUSSION

In 1949, Stout and Murray^[13] first described hemangiopericytoma (now called SFTs in the WHO classification 2021) as a rare vascular neoplasm. SFTs are aggressive tumors that tend to recur locally or distantly as extraneural distant metastases.^[6] CNS SFTs are uncommon and their extraneural distant spread to the spine is rarely reported.^[6,11] In 1961, Kruse^[5] reported intracranial SFTs that metastasized to the spine. Spinal metastasis usually occurs by one of three routes: Via lymphatic, direct extension, and hematogenous pathways.^[6] Valve-less connections between the intracranial venous system and the paravertebral venous plexus are the main pathways for spinal metastases.^[6,13] Differential spinal SFT diagnoses include malignant schwannoma, neuroblastoma, neurofibroma, and meningioma.^[11] In our case, although there was no local intracranial recurrence, and her surveillance PET scan was negative, isolated spinal metastasis still occurred after a 2-year latency period.

A PET scan is a useful tool to detect osseous metastasis at an early stage of disease progression, but a single negative scan may not be enough.^[6] The usual appearance of SFTs spinal metastasis is isointense to bone marrow on T1- and T2-weighted MR images, with homogeneous contrast enhancement, and the epicenter of the disease is usually in the vertebral body.^[9,11] Typical angiographic findings are a hypervascular mass with irregular, “corkscrew” vessels with a prolonged tumor blush and slow circulation time.^[12] In our case, an MRI scan showed a retropulsed C7 vertebra, intense post-gadolinium enhancement with an extension to posterior elements.

The management of spinal metastatic SFTs remains controversial, and surgical resection is the mainstay of treatment. There is no consensus on the extent of resection due to osseous invasion, and the proximity of vital neural tissues, especially in the cervical spine metastases.^[8,11] Pre-operative embolization has been used to reduce the risk of significant bleeding and facilitate maximal resection.^[12] Gamma Knife and CyberKnife have promising results as they increase survival and delay local recurrence.^[2] Gross total resection followed by adjuvant RT seems to be the best contemporary treatment strategy.^[2,4] High-precision RTs, such as fractionated stereotactic RT and intensity-modulated RT, are effective and safe.^[2] Radiosurgery and intensity-modulated RT can be considered in the setting of prior radiation, but chemotherapy remains controversial.^[4,11] The prognosis is poor once distal metastases have occurred and spinal metastases are, in particular, a rapidly progressive disease with acute neurological deficits.^[9] Combs et al.^[2] analyzed the use of high-precision RT (combined with surgical resection) in SFTs, including 2 spine cases, and demonstrated a survival rate of 100% at 5 years and 64% at 10 years.

It has been postulated that once the local cranial control of SFT is mitigated meticulously, spinal metastasis is likely to manifest due to a higher propensity for hematogenous spread via its peculiar valve-less angio-architecture.^[1,5,6,8] Extraneural metastasis can occur with a different latency period which can be as much as several years, even though the primary lesion has been well controlled.^[5] In our case, this latent period was 2 years, but it has been reported as long as 11 years.^[14] Spinal metastasis should be kept in mind when a patient with adequately treated intracranial SFT presents with back or neck pain and/or is accompanied by limb weakness. Unfortunately, once symptomatic spinal metastases are diagnosed, there is no satisfactory treatment modality to stop their progression, and the prognosis remains poor.^[3,14] Therefore, it is essentially necessary to alert patients about possible spinal metastasis and the need for an extended clinical follow-up. The optimal strategy for surveillance is controversial, and a standard interval for serial imaging has not been established.^[4,6,10,13]

CONCLUSION

Intracranial SFTs are uncommon tumors with only a few reports of cervical spine involvement. Once a local cranial disease is well controlled by a diligent treatment strategy, there is a likely possibility of acutely progressive spinal metastatic disease even after a long latency period. This underscores the need for a pre-emptive strategy for serial imaging of the spine at regular intervals with appropriate counseling of patients to be vigilant for subtle clinical manifestations to ensure an early prompt diagnosis and management.