# Recurrent Solitary Fibrous Tumor in Intradural Extramedullary Space: Case Report and Review of the Literature

Authors: Neris Dincer; Melisa Bagci; Metin Figen; Adem Yilmaz; Ahmet Mesrur Halefoglu; Canan Tanik; Esengul Kocak Uzel
Journal: Case Reports in Oncological Medicine
 (2021)

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## Abstract

Solitary fibrous tumor/hemangiopericytoma (SFT/HPC) is a rare neoplasm arising from spindle cells and most commonly arising from pleura. Spinal SFT/HPC is a rare entity; hence, it is not on the top of the differential diagnosis list when a clinician faces a spinal lesion. In the review of the literature, there exist less than 50 case reports of intradural extramedullary SFT/HPC. Here, we present a 54-year-old female patient who underwent subtotal surgical excision of an intradural extramedullary spinal mass pathologically reported to be SFT/HPC and had symptomatic recurrence in the 3rd year of follow-up. Surgical intervention was unachievable and the patient was given 45 Gy to the surgical cavity followed by a 5.4 Gy boost to visible tumor with external radiotherapy. Patient reported significant relief of her symptoms. We aim to contribute to the formation of a treatment algorithm for this rare entity.


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## Body

## 1. Introduction

Solitary fibrous tumors (SFT) (formerly known as hemangiopericytoma (HPC)) are rare mesenchymal neoplasms originating from spindle cells [1]. Although the majority arise from pleura, 60% of SFTs originate outside the pleura [2], and SFTs are deemed to arise anywhere in the body. CD34 is a sensitive marker though it is not specific, and lately specific markers are identified [3]. Although surgery with negative margins is the mainstay treatment, the role of chemotherapy and radiotherapy is under debate [4]. This report presents a case of intradural extramedullary (IDEM) SFT in the thoracic spine.


## 2. Case Report

Our patient is a 54-year-old female with a past medical history including asthma and peptic ulcer disease. Her family history is free of malignant diseases. In 2016, patient’s chest X-ray examination found a suspicious lesion. Magnetic resonance imaging (MRI) was ordered for further investigation in November 2017 since the patient was complaining of back pain. MRI revealed a spinal lesion12×10mm in diameter at the level of second thoracic vertebra (T2) (Figures 1(a) and 1(b)). The patient was referred to surgery and one month later underwent total laminectomy at the level of second thoracic vertebra (T2) and subtotal excision of intradural extramedullary lesion with neuromonitoring. The lesion involved nerve roots; complete resection could not be achieved due to perioperative neuromonitor signals. Postoperative neurological examination showed motor strengths as 3/5 for the left thigh, 3/5 for the left knee, 0/5 for the left foot, and 4/5 for the left hand. Patient was started on corticosteroid. Left lower extremity strength improved to 4/5, and the patient was discharged on postoperative day 4. A follow-up physical examination and MRI examination were planned for the patient 45 days after the surgery. Pathology report confirmed a WHO 2016 Grade 1 solitary fibrous tumor positive for CD34 and negative for S100, epithelial membrane antigen (EMA), and p53 (Figure 2). Thereafter, the patient underwent routine follow-up. MRI was performed 45 days after the surgery, and it was consistent with a remnant paracentral mass (Figures 1(c) and 1(d)). Control MRI a year after showed regression of the lesion (Figures 1(e) and 1(f)). In June 2020, no intraspinal mass lesion was revealed on MRI. In January 2021, the patient came for routine follow-up with a complaint of bilateral pain in her upper extremities as well as back pain. MRI examination of the patient was consistent with an intradural extramedullary lesion 10×5mm in diameter which was compressing the spinal canal in the left paramedian area at the level of T2.Figure 1
MRI images on preoperative, 3 months postoperative, 1 year postoperative, and current period. (a, b) (08.12.2017) Preoperative MRI reveals a lesion12×10mm in diameter, hypointense in both T1-w and T2-w, heterogeneously contrast enhancing with gadolinium. (c, d) (06.03.2018) Postoperative MRI reveals a paracentral mass located in the posterior edge of the spinal canal with minimal contrast enhancement. (e, f) (19.01.2019) Control MRI reveals. (g, h) (18.02.2021): MRI at current presentation reveals a lesion which is moderately hypointense in T1-w and hypointense in T2-w with homogeneous contrast enhancement.
(a)(b)(c)(d)(e)(f)(g)(h)Figure 2
Pathology slides. (a) Hematoxylin and eosin staining of z200 magnification reveals spindloid nuclei and thin vascular structures. (b) Diffuse staining with CD34 at ×200 magnification. (c) 1-2% proliferation index with Ki-67 at ×200 magnification.
(a)(b)(c)The patient was presented at the multidisciplinary tumor board for treatment options. Given the critical anatomic location and close involvement with nerve roots, the patient was found unsuitable for surgery. Eventually, the board decided on the referral to the radiation oncology clinic. A repeat contrasted thin-slice MRI of cervical and thoracic spine was performed (Figures1(g) and 1(h)). The report confirmed the recent findings. Patient underwent 1 mm thin slice treatment-planning computer tomography (CT) with intravenous contrast infusion. CT-MRI image fusion was acquired with the preoperative and present MRI for better discrimination of the resection cavity and the boundaries of the present lesion to achieve improved target delineation for treatment planning [5]. Gross tumor volume (GTV) was defined as the postoperative surgical cavity and clinical target volume (CTV) was extended 2 cm above and below the GTV. Planned RT dose was 45 Gray (Gy) in 25 fractions (1.8 Gy/fraction) and a boost of 5.4 Gy in 3 fractions (1.8 Gy/fraction). Organs at risk (OAR) were determined as the spinal cord, lungs, and esophagus in accordance with the atlas of dose constraints in thoracic radiotherapy published by Kong et al. [6]. Maximum point dose constraint to the spinal cord was determined to be 45 Gray (Gy) in accordance with the Quantitative Analyses of Normal Tissue Effects in the Clinic (QUANTEC) model to avoid any radiation-related side effect, namely, myelopathy [7]. Treatment planning was done with conformal three-dimensional (3D), intensity-modified radiation therapy (IMRT), and volumetric modulated arc therapy (VMAT, hereinafter referred to as ARC) approach, respectively (Figure 3). QUANTEC normal tissue tolerances were taken into consideration and the calculations were made accordingly (Table 1) [8]. ARC was the chosen modality with optimal spinal cord protection compared to 3D and tolerable treatment duration for patient comfort and cooperation to stand immobile during the treatment compared to IMRT.Figure 3
Plan summations and dose volume histogram (DVH) of 3DCRT, IMRT, and ARC. (a) Plan summations on axial (upper left), frontal (lower left), and sagittal (lower right) views and DVH graph (upper right) of conformal three-dimensional plan. Outer red line of plan summations represents 50% (25.2 Gy) isodose line, green line represents 42.84 Gy, and blue line represents 50.4 Gy. Red dots represent maximum point doses on each view. (b) Plan summations on axial (upper left), frontal (lower left), and sagittal (lower right) views and DVH graph (upper right) of intensity-modulated radiation therapy plan. Outer red line of plan summations represents 50% (25.2 Gy) isodose line, green line represents 42.84 Gy, and blue line represents 50.4 Gy. Red dots represent maximum point doses on each view. (c) Plan summations on axial (upper left), frontal (lower left), and sagittal (lower right) views and DVH graph (upper right) of volumetric modulated arc therapy plan. Outer red line of plan summations represents 50% (25.2 Gy) isodose line, green line represents 42.84 Gy, and blue line represents 50.4 Gy. Red dots represent maximum point doses on each view.
(a)(b)(c)Table 1
Comparison of treatment plans.
PTVSpinal cordLungEsophagusMonitor unit (MU)D50 (cGy)D98 (cGy)D2 (cGy)D2 (cGy)V20 (%)V5 (%)Mean (cGy)33% (cGy)Mean (cGy)3D53705090546854371.712.5230839562455IMRT (5 field)51825067530252262101903852551353ARC520049505333522011220754032610603D: conformal three-dimensional; IMRT: intensity-modified radiation therapy; ARC: volumetric modulated arc therapy; PTV: planning target volume; D95: dose covering 95% of the PTV; D50: median dose, D98: near-minimum dose, D2: near-maximum dose; cGy: centigray; V20: lung volume that received a dose of 20 Gy or more; V5: lung volume that received a dose of 5 Gy or more; 33%: dose received by 33% of esophagus.


## 3. Discussion

Primary spinal cord tumors are rare neoplasms that constitute 4.5% of central nervous system (CNS) tumors in adults [9]. Their primary treatment is surgical resection if possible [10], and radiotherapy can ensue if total resection is not achieved [11]. They are classified according to their location as extradural, intradural extramedullary and intramedullary. Extradural tumors are most common followed by intradural extramedullary (IDEM) tumors. Meningioma, schwannoma, and neurofibroma comprise the majority of intradural extramedullary tumors [12]. Solitary fibrous tumors of intradural extramedullary space is a rare entity. They correspond to the group IIA in the classification of Liu et al. [13] (Table 2). The majority of type IIA spinal SFTs arise at the thoracic spine [12]. Table 3 summarizes the cases present in the PUBMED database.Table 2
Liu classification for localization of spinal SFTs [13].
TypeSubtypeType 1: extraduralIA, intracanal typeIB, intra- and extracanal typeType II: intraduralIIA, extramedullary typeIIB, intramedullary invasion typeType III: intra- to extradural and paravertebral typeTable 3
Reported cases of spinal intradural extramedullary solitary fibrous tumor/hemangiopericytoma.
Case report, yearAge/sexChief complaint at presentationLevelT1-WT2-WContrast enhancementTreatmentRT regimen (if performed)OutcomeTreatment of recurrencePitlyk et al., 1965 [36]39/MTotal paraplegiaT8N/AN/AN/AGTRN/ATumor recurred 4 times in 8 yearsReoperationPitlyk et al., 1965 [36]60/MParesthesia and weakness of RLC4N/AN/AN/AGTRN/AN/APitlyk et al., 1965 [36]49/FLeft-sided weakness and paresthesiasC3N/AN/AN/AGTRN/A10 years NED—Kitanaka et al., 1993 [37]59/FGait disturbanceT6IsointenseN/AHomEEBRN/A16 months NEDMalek et al., 1997 [38]33/MBack painProgressive myelopathyLE dysesthesiasT7-T8—HypointenseMild enhancementResection, NSN/AN/AKanahara et al., 1998 [39]62/MSensory disturbance of bilateral lower extremityC6-C7HypointenseHypointenseMarginal enhancementGTRN/AN/ABrunori et al., 1999 [40]46/FLeft sciatalgiaT12-L1T1 görüntüNSHomEGTRN/A4 months NEDVorster et al., 2000 [41]51/MBurning sensation and numbness in both thighs weakness in the LLET2-T3Well-circumscribed mass at T2–3, which enhanced homogeneously on T1-weighted MR imaging with gadoliniumNSHomEGTRN/A7 months NEDKurtkaya et al. 2001 [42]70/FRL weaknessT3Irregular isointensityIrregular hypointensityECRN/ANo recurrence until the reportDufour et al., 2001 [43]45/MParaparesisCervical (not specified)N/AN/AN/ACRN/A2 years NEDDufour et al., 2001 [43]18/FDorsalgiaThoracal (not specified)NMN/AN/ASTR + RT40 GyAlive after 4.6 years of f/uDufour et al., 2001 [43]43/FIntercostal neuralgiaThoracal (not specified)NMN/AN/ACRN/A4.1 years NEDDufour et al., 2001 [43]38/MIntercostal neuralgiaThoracic (NS)N/AN/AN/ACR + RT40 Gy12.8 years NEDBetchen et al., 2002 [44]31/MB/L leg paresthesiaLE cramping and fatigueL4Intermediate signalIncreased signalDiffuse enhancementEBRN/ANo recurrence at the timePizzolitto et al., 2004 [45]36/MParesthesias of right footLE weaknessUrinary loss and rectal incontinenceT7/T8NSNSHomECRN/A12 months NEDBohinski et al., 2004 [46]49/FNeck pain and stiffnessC4İsointenseHypointenseHomEEBRNA10 months NEDPiana et al., 2004 [47]67/MLumbar painWeakness in RLEL1-L2NSNSHetEGTR———Ogawa et al., 2005 [48]63/FSensory disturbance of LET11Mildly hypointenseHypointenseHomEGTR—18 months NED—Pakasa et al., 2005 [49]27/MBack painT5-T7———STR—Recurrence after 14 yearsSurgeryMunoz et al., 2008 [33]35/MHypoesthesiaSacral———CR—Pulmonary mets at 4th yearObservationNew nodules and lumbosacral recurrence at the 6th yearPalliative RTNew metastatic lesions in lungs and liver at the 7th yearChemotherapyFitzpatrick et al., 2009 [50]54/MLeft paraspinal, buttock, and anterolateral thigh pain radiating down the anterior shin and left footL4-L5Soft tissue signal intensitySoft tissue signal intensityNSGTR + RTNSN/AArantes et al., 2009 [22]22/MDorsal pain associated with B/L hypoesthesia and weakness of the LET1-T2IsointenseIsointenseHomEGTR—18 months NEDMoscovici et al., 2011 [51]20/MMild thoracic back pain radiating to the LL progressive paraparesis fecal and urinary incontinenceT9-T10IsointenseIsointenseHomEGTRPatient was referred to RT but declined and went with imaging and clinical follow-upPatient declined the treatment2 years NEDAckerman et al. 2011 [52]58/MAcute weakness of the LE bladder and bowel incontinenceT10IsodenseHyperdenseEEBR—N/AKirkbride et al., 2011 [53]72/MAcute urinary retentionC3NSModerately hyperintenseHomECR———Bisceglia et al. [54]47/MWeakness in RLET3-T4NSNS—GTR—11.6 years NED—Brigui et al., 2012 [55]56/MNeuropathic pain of the RLE LL pain and gait difficultiesT6-T7IsointenseIsointenseHomEGTR—29 months NEDMariniella et al., 2012 [56]67/MPain dysesthesia and weakness in left arm and legC4-7IsointenseHypointenseHomEGTR—1 year NEDShirzadi et al., 2013 [31]49/MPatient with a history of SFT presented with left LE weakness and B/L radicular painT9-T12NSNSEDebulking—Recurred in postoperative month 4 with multiple metastasesNo interventionShirzadi et al., 2013 [31]57/MLower back painT9-T10NSNSEPreoperative embolization followed by microdissection + adjuvant RT(IMRT of 5580 cGy over 48 elapsed days) to his resection cavity3 years NEDShirzadi et al., 2013 [31]56/MNeck discomfort radiating into head and both shouldersC1-C3NSNSEGTRRadiosurgery was performed on recurrence (month 6- T2-3 level)3 years NEDDrazin et al., 2013 [34]56/MNeck pain radiating to head and shouldersC0-C4NSNSECR—Metastasis at T2-T3 6 months postoperativeRadiosurgeryLee et al., 2013 [57]21/MNeck painB/L tingling sensation in both handsC1-C2IsointenseHyperintenseHomECR—1 year NEDKobayashi et al., 2014 [58]40/MGait disturbance and numbness in both handsC4-C5HypointenseNSHomEResection, NS—Recurrence after 17.7 yearsSTRSade et al., 2015 [59]43/MWeakness of LENSHypointenseHomEResection, NSN/ANMDas et al., 2015 [60]50/MQuadriparesis, numbness in B/L UEC4-C5NSNSEGTR + adjuvant RT (EBRT) + adjuvant CTNS23 months NEDDas et al., 2015 [60]12/FParaparesisT11-L1NSNSEGTR + RTNS9 months NEDKaur et al., 2015 [11]16/MLoss of strength in LET9N/AN/AN/AExcision, NS followed by RTf 45 Gy in 25 fractions over a period of 5 weeks5 years NEDBasaran et al., 2015 [61]67/MWalking disabilityL3NSHypointenseHomESurgery, NS—12 months NEDBiswas et al., 2017 [62]35/FBackacheLE weaknessT10-T11HypointenseHyperintenseNMSTR + metastasectomy20 Gy in five fractions over 1 week to the primary residual siteChew et al., 2017 [63]63/MBack painParaparesisSensory deficit of LET9NSNSEGTRN/A12 months NEDAlbert et al. 2017 [64]10/MRUE weaknessC1-C3HypointenseHypointenseHomEGTR—1 year NED—Tomamatsu et al., 2019 [65]68/FIncidental lesion on imagingT9IsointenseHypointenseHetEGTRN/A3 years NEDWang et al. 2019 [18]21/MBackacheT3-T4NSSlightly hyperintenseNSGTR + RTNot specified for the patient; median dose is 40 Gy (35-45 Gy)96 months NEDWang et al. 2019 [18]43/FBackacheT8NSSlightly hyperintenseNSGTR + RTNot specified for the patient; median dose is 40 Gy (35-45 Gy)Recurrence 49 month postoperativelyRTWang et al. 2019 [18]35/FNeck painUE numbnessC4-C6NSSlightly hyperintenseNSSTRN/ARecurrence at month 32 postoperativelyNo treatmentWang et al. 2019 [18]33/FBackacheT9NSSlightly hyperintenseNSGTR + RTNot specified for the patient; median dose is 40 Gy (35-45 Gy)70 months NEDWang et al. 2019 [18]57/MBackacheT3-T4NSSlightly hyperintenseNSGTRN/A67 months NEDWang et al. 2019 [18]37/FBackacheT6NSSlightly hyperintenseNSGTRN/ARecurrence at month 22 postoperativelyRTWang et al. 2019 [18]40/FBackacheLE weaknessT11-t12NSSlightly hyperintenseNSSTR + RTNot specified for the patient; median dose is 40 Gy (35-45 Gy)42 months NEDWang et al. 2019 [18]49/MBackacheT4NSSlightly hyperintenseNSGTRN/A35 months NEDWang et al. 2019 [18]34/FNeck discomfortC6-c7NSSlightly hyperintenseNSGTRNot specified for the patient; median dose is 40 Gy (35-45 Gy)24 months NEDMurata et al., 2020 [35]49/FChest painT6İsointenseHypointenseNSGTR—Recurrence at 12 month postoperativelyCarbon ion radiotherapy-64 GyKim et al., 2020 [66]64/MRL painHypointenseHypointenseHetESurgical removal, NSN/A1 year NEDGlauser et al., 2020 [67]72/MLE weakness, pain and numbnessC5-C7T1w hypointense (?)NSNSGTRN/AN/ASingla et al., 2020 [68]50/MQuadriparesis, numbness in B/L UEC4-C5N/AN/AN/AGTR + adjuvant RT + adjuvant CTNot specifiedRecurrence at 62 months postoperativelySingla et al., 2020 [68]12/FAcute conus cauda syndromeT11-L1N/AN/AN/AGTR + adjuvant RTNS52 months NEDSingla et al., 2020 [68]38/MSpastic paraplegia bladder dysfunctionC7-T1N/AN/AN/AGTRN/A50 months NEDKoduru et al., 2020 [69]16/FWeakness of RUE and RLEC5-C7HypointenseHyperintenseHomECRN/AN/ADauleac et al., 2020 [70]67/MAsthenia and weakness RLET8-T9NSHyposignalNSCRN/A1 year NEDAbbreviations are as follows: M: male; F: female; LE: lower extremity; RLE: right lower extremity; LLE: left lower extremity; UE: upper extremity; RUE: right upper extremity; LUE: left upper extremirt; LL: left leg; RL: right leg; B/L: bilateral; C: cervical; T: thoracal vertebra; L: lombar vertebra; HomE: homogenous enhancement; HetE: heterogenous enhancement; E: enhancement (not specified) GTR: gross total resection; STR: subtotal resection; CR: complete resection; EBR: en bloc resection; NS: not specified; RT: radiotherapy; CT: chemotherapy N/A: not applicable NED: no evidence of disease; Gy: gray.Due to their rareness, SFTs are not on the top of the differential diagnoses list when the clinician is faced with a lesion in the spinal cord [14]. MRI is the preferred modality to delineate the tumor and evaluate for invasion, but the imaging findings are variable and nonspecific [15]. Nevertheless, the diagnosis is less of a challenge with the advances in knowledge in pathological markers. CD34, although not specific, is deemed to be the histological hallmark of SFTs and has been found to be expressed in 79% of cases [16, 17]. A retrospective study with 16 SFTs located in the spinal cord confirmed this finding with 100% SFTs being positive for CD34 and negative for EMA, GFAP, and MBP staining. S-100 positivity varied with 5 of the patients staining positive [18]. Lately, STAT6 and GRIA2 are proposed to be distinguishing markers for SFTs [19, 20]. STAT6 expression is driven by NAB2-STAT6 gene fusion, and STAT6 has lately been sought to be a specific marker for SFT [19, 21, 22]. STAT6 positivity in SFTs and HPCs is considered as finding that supports the abolishment of the thin boundary between these 2 entities in late 1990s [3, 23, 24].Achieving complete surgical resection is the main goal in extrathoracic SFTs, and it is associated with improved local control and survival. Routine long-term follow-ups must be ensured for the early detection of recurrence [25]. Although there are no standardized follow-up routines for these patients. The anatomical location of the tumor may not allow the total resection in some cases [4]. The role of radiotherapy is under debate in SFTs. There are studies advocating that RT is not strictly indicated after complete resection due to close follow-up and low recurrence rate [4] and that adjuvant radiotherapy can be considered in the case of subtotal resection [26–28] or if we are facing a high grade SFT [29]. There are studies advocating adjuvant radiotherapy be standard of treatment [18, 30]. Complete resection, low-grade tumor and young age were reported to be factors that led the clinicians to omit radiotherapy [31]. Krengli et al. revised 151 extrathoracic SFT patients while Wang et al. reviewed 16 spinal SFT patients in terms of the effect of GTR vs. GTR+RT on local recurrence (LC), disease-free survival (DFS), and overall survival (OS), and they both came up with the same conclusion: addition of adjuvant RT improved LS and DFS while GTR was the main predictor of OS [18, 32]. While a retrospective review reveals that the median radiation dose for extracranial SFTs is 60 Gy [32], this dose seems to be unachievable in the spinal SFTs due to dose constraints of the spinal cord, which is 45-50 Gy. Retrospective single center study of Wang et al. reported a median dose of 40 Gy in patients with spinal SFT [18]. The treatment plan must be tailored according to location and extent of the tumor. Radiation doses may vary in between patients if the plan cannot limit spinal cord doses in the desired limits.Herein, we present a case of IDEM SFT who had STR 27 months prior to presentation to our clinic with bilateral pain over the arms and legs and newly developed radiological evidence of recurrence. Radiotherapy was the treatment of choice for this patient due to the location of the tumor. To our knowledge, we present the 5th case of a recurrent SFT treated with radiotherapy [18, 33–35].


## 4. Conclusion

Spinal type IIA SFT is a rare entity with less than 50 case reports in the literature. GTR is the required treatment option while the role of adjuvant radiotherapy and its indications is yet to be discussed. We contribute to the literature by presenting a rare case in which close follow-up ensued STR, and radiotherapy was performed when the lesion recurred. We believe that the increase in the number of cases in the literature will help and contribute to the embodiment of the therapeutic algorithm of the disease in question.



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