Solitary fibrous tumors of the spine: a pediatric case report with a comprehensive review of the literature

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  • 1 Division of Neurosurgery, Arkansas Children's Hospital; and 
  • | 2 Departments of Neurosurgery and
  • | 3 Pathology, University of Arkansas for Medical Sciences, Little Rock, Arkansas
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Solitary fibrous tumors of the spine are rare lesions. Their description in the literature is limited to case reports and small case series. While generally benign lesions, they can recur and occasionally occur as malignancies. Here the authors present the case of a 10-year-old boy, the youngest patient and first preadolescent reported thus far, with this condition. In addition, they perform a comprehensive review of all previously published cases of spinal solitary fibrous tumors.

ABBREVIATIONS

CNS = central nervous system; GTR = gross-total resection; SFT = solitary fibrous tumor; STR = subtotal resection.

Solitary fibrous tumors of the spine are rare lesions. Their description in the literature is limited to case reports and small case series. While generally benign lesions, they can recur and occasionally occur as malignancies. Here the authors present the case of a 10-year-old boy, the youngest patient and first preadolescent reported thus far, with this condition. In addition, they perform a comprehensive review of all previously published cases of spinal solitary fibrous tumors.

ABBREVIATIONS

CNS = central nervous system; GTR = gross-total resection; SFT = solitary fibrous tumor; STR = subtotal resection.

Solitary fibrous tumors (SFTs) were initially described by Klemperer and Rabin in 1931.36 These lesions are most commonly found in the pleura and abdomen/pelvis. One large single-center review suggests a nearly even split between benign and malignant pathologies.19 A recent review of the Surveillance, Epidemiology, and End Results (SEER) database found 804 cases reported over nearly 40 years. Tumors in these patients were thoracic/abdominal/pelvic in 35.3%, central nervous system (CNS) in 24.5%, head/neck in 19.9%, and extremity in 16.2%. Most reported cases did not include pathological classification, and a plurality of patients (49.4%) underwent surgery without adjuvant therapy.79

Carneiro and colleagues described the first 2 cases of spinal SFT, both of which were treated with surgery.12 Few comprehensive reviews of these lesions exist. Bisceglia et al. found 220 cases of CNS SFTs, 50 of which occurred in the spine.5 Fargen et al. reviewed 189 cases of CNS SFTs, including 46 spinal SFTs, and added 1 other spinal SFT case from their own experience.22

Spinal SFT in pediatric patients is quite rare. The youngest patient with spinal SFT reported thus far was a 17-year-old male,30 and there have been only 2 other previously reported cases of spinal SFT in patients younger than 21 years of age.11,71 Here we describe the case of an intradural extramedullary spinal SFT in a 10-year-old boy. In addition, we identified 81 unique patients with spinal SFT in the literature and comprehensively review these reports.

Case Report

History and Examination

A 10-year-old, previously healthy male was admitted to the neurology service for evaluation of right upper extremity weakness. On examination, he was unable to adduct his right shoulder and had Medical Research Council Grade 4/5 strength in the other muscle groups of his right upper extremity. Otherwise, his motor and sensory examinations were normal. He was hyperreflexic in the right upper and lower extremities with a positive Babinski sign on the right. Magnetic resonance imaging studies revealed an intradural extramedullary tumor on the right side at C1–3 that was hypointense on T1- and T2-weighted sequences with homogeneous enhancement (Fig. 1A–C). Preoperative diagnosis was meningioma or, less likely, nerve sheath tumor.

FIG. 1.
FIG. 1.

Preoperative axial T2-weighted MR image (A) demonstrating hypointensity of the lesion and cord compression. Preoperative sagittal (B) and coronal (C) T1-weighted MR images with contrast demonstrating homogeneous enhancement of the tumor. Postoperative coronal T1-weighted MR image (D) with contrast demonstrating GTR and reexpansion of the spinal cord.

Operation

The patient was taken to surgery where a C1–3 laminectomy was performed for excision of the tumor. After performing two-thirds laminectomies at each level, a paramedian durotomy was made. The firm, rubbery pale tumor was intradural extramedullary without dural attachment. It was located between the dorsal and ventral nerve rootlets. It was adherent to the lateral aspect of the spinal cord but could be dissected free of pia mater without injury to the cord and did not have an intramedullary component. The tumor had a pial attachment at its caudal end. The tumor also appeared to be attached to the right dentate ligament at C-1. Gross-total resection (GTR) was achieved in a piecemeal fashion (Fig. 2). There were no intraoperative complications.

FIG. 2.
FIG. 2.

Intraoperative photographs of tumor resection. A: Initial view of tumor with dorsal nerve roots overlying the lesion. B: Pial attachment at caudal end of tumor. C: Attachment of tumor to pia of spinal cord. D: Tumor has been completely resected. Figure is available in color online only.

Postoperative Course

Postoperative MRI confirmed GTR (Fig. 1D). The patient was discharged home on postoperative Day 4 with outpatient physical therapy. At the time of discharge, he had trace residual weakness in his right hand and otherwise had full strength with no new neurological deficits. At 4.5 months after surgery, he had regained full strength, MRI showed no evidence of recurrent disease, and dynamic cervical spine radiographs showed no evidence of instability (Fig. 3). One year after surgery, the patient had a normal neurological examination, no evidence of recurrence on MRI, and maintained stability on flexion and extension radiographs of the cervical spine.

FIG. 3.
FIG. 3.

Postoperative flexion (A) and extension (B) cervical spine radiographs demonstrating no evidence of dynamic instability.

Light microscopy examination of the tissue showed a spindle cell neoplasm with alternating cellular and collagenous areas. A few blood vessels were well demarcated with thin walls and showed branching, that is, staghorn vessels (Fig. 4A–C). A few nuclei had nucleoli, but the cell population was overall monomorphous without significant cytological atypia. Mitotic count was variable between 1 and 5/10 hpf on multiple counts in different areas. No necrosis, hemorrhage, or hypercellularity was seen. The neoplasm was diffusely and strongly positive for Bcl-2 and CD34 (Fig. 4D) with a diffuse nuclear staining for STAT6 (Fig. 4E). The Ki-67 proliferation index was variable between 10% and 15% in various areas (Fig. 4F). Epithelial membrane antigen and S100 protein were negative. This appearance was consistent with SFT with atypical features.

FIG. 4.
FIG. 4.

Microscopic findings. A: Low-power view with peculiar, well-defined, branching blood vessels (asterisk) and alternating dark and light areas reflecting variable cellularity and collagen. B: Spindle cell morphology of the neoplastic cells and mitotic activity (arrow). C: Thick, keloid-like collagen bundles and decreased cellularity in some areas. D: Diffuse and strong CD34 positivity. E: Nuclear STAT6 expression. F: Higher-than-expected Ki-67 proliferation index. H & E (A–C), original magnifications ×40 (A), ×200 (B–C), ×100 (D–F). Figure is available in color online only.

Review of the Literature

A PubMed search was performed for SFTs of the spine. In addition, the reference section of each paper was reviewed, allowing for the identification of additional cases. We identified 65 previously published papers with 83 cases.1–4,7–14,16,17,20–22,24–35,37–40,42,43,46–59,62,64–74,76,78,80,81 Two of these papers clearly duplicated patients (4 reports of 2 unique patients).14,76 A third reported patient was a suspected duplication.12,57 Eliminating these duplications and adding our own report yielded 82 reported cases of spinal SFT (Table 1).

TABLE 1.

Literature summary of spinal SFT cases

Authors & YearAge (yrs)/SexLevelCompartmentTreatmentHistologyLast FU (yrs)OutcomeNotes
Carneiro et al., 199650/FNRIDEM & IDIMSTRSFT6.0RecurrenceDied 1 wk after surgery for recurrence
54/FLumbarNRGTRSFT7.0Disease freeDied of unrelated causes
Alston et al., 199747/MT4–5IDIMGTRSFT0.2Disease free
Kuchelmeister et al., 199764/MC-5IDEM & IDIMGTRSFTNRNR
Malek et al., 199733/MT7–8IDEMGTRSFTNRNR
Brunori et al., 199918/MO–C3ED & IDEMGTRSFT1.0Disease free
46/FT12–L1IDEMGTRSFT0.3Disease free
Hasegawa et al., 199939/MNRNRGTRSFT9.0Local recurrence at 5 yrs & 9 yrs
Kanahara et al., 199962/MC6–7IDEM & IDIMSurgerySFTNRNR
46/FC4–5ED & IDEMGTRSFTNRNR
Donnellan et al., 200039/ML-1EDGTRSFTNRNR
Mordani et al., 200033/MC-5IDIMGTRSFT1.5Disease free
Vorster et al., 200051/MT2–3IDEMGTRSFT0.6Disease free
Kurtkaya et al., 200170/FT-3IDEMGTRSFT1.0Disease free
Endo et al., 200363/FC2–4EDGTRSFTNRNRDumbbell tumor
Obara et al., 200349/FC2–4EDGTR + preop emboSFT1.0Disease freePrimarily extraspinal
Tihan et al., 2003NRNRIDIMNRNRNRNR
NRNRIDIMNRNRNRNR
NRNRIDEMNRNRNRNR
NRNRIDEMNRNRNRNR
Bohinski et al., 200449/FC-4IDEM & IDIMGTRSFT w/ focal pleomorphism0.8Disease free
Caroli et al., 200454/MC7–T1IDEMGTRSFT1.3Disease free
Hirakawa et al., 200452/MC1–2EDGTRSFT2.5Disease freePrimarily extraspinal
Kawamura et al., 200464/MT2–3IDEM & IDIMSTRSFT0.5No progression
Kim et al., 200455/MC-6, T-3, T4–5, L-5, S-2EDSTRMalignant SFTNRNRPrior posterior fossa tumor
Piana et al., 200467/ML1–2EDGTRSFTNRNR
Pizzolitto et al., 200436/MT7–8IDEMGTRSFT1.5Disease free
47/MC-4IDIMGTRSFT1.0Disease free
Miyashita et al., 200463/FC-7, T3–5IDEMGTR (1 lesion)SFTNRStable residueT-5 lesion resected, had tentorial lesion 15 yrs prior
Jallo et al., 200541/MC6–7IDIMGTRSFT3.5Disease free
17/MT-5, T-6IDIMGTRSFT1.6Disease free2 separate lesions
59/MT-5NRGTRSFT4.8Disease free
37/FT2–3NRGTRSFT5.0Disease free
Ogawa et al., 200563/FT-11IDEMGTRSFTNRNR
Ogungbo et al., 200553/MC3–4IDEM & IDIMGTRSFTNRNR
Pakasa et al., 200527/MT5–7IDEM & IDIMSTRSFT14.0New sacral lesion at 14 yrs treated w/ GTR
Metellus et al., 200756/MC7–T1NRSTRSFT3.5Local progression at 2 yrs treated w/ GTR
57/ML-2NRGTRSFT8.5Recurred at 8.5 yrs, treated w/ GTR & chemo
57/MT-9NRGTRSFT1.8Disease free
44/FT-12NRGTRSFT4.2Disease free
72/FT-12NRGTRSFT0.8Disease free
44/FT-7NRGTRSFT1.7Disease free
Nakamura et al., 200728/FCervicalEDGTRSFT5.0Disease freeArising dorsally from lamina & facets
Hashimoto et al., 200871/FC4–5EDSTR + anterior fusionSFT4.0Progressed at 6 mos & 2.5 yrsRequired additional resection & fusion surgeries
Muñoz et al., 200835/MSacralNRGTRSFT8.0Local recurrence w/ pulmonary mets at 5.5 yrsMalignant pulmonary mets at 3.5 yrs; pulmonary/hepatic mets at 6.5 yrs
Shin et al., 200840/FC6–7ED & IDEMGTRSFT0.7Disease freeDumbbell tumor
Arantes et al., 200922/MT1–2IDEMGTRSFT1.5Disease free
Ciappetta et al., 201075/FT6–7IDEM & IDIMGTRSFT2.0Disease free
Ishii et al., 200963/FC-5IDIMGTRSFT1.2Disease free
Kakimaru et al., 200975/FT8–10EDGTR + dorsal fusionSFT3.0Disease freeDumbbell tumor w/ large extraspinal component
Aftab et al., 201038/ML4–S2EDSTRSFT w/ lipomatous features0.4Stable residue
Cincu et al., 201058/MT3–5IDEMGTRSFTNRNR
Vassal et al., 201152/FT8–9ED & IDEMGTRSFT5.2Disease free
Fargen et al., 201162/MO–C2IDEMGTRSFT0.5Disease free
28/FC2–3IDEM & IDIMGTRSFT2.0Small radiographic recurrenceLost to FU
Guo et al., 201260/MThoracicIntracanalSurgeryMalignant SFT0.2Deceased from metastatic diseaseMetastatic from renal primary
Takenouchi et al., 201145/FC-3, C7–T1IDEMGTR (1 lesion)SFT0.4Stable residuePrior posterior fossa tumor
Bouyer et al., 201256/FT10–11EDSTRSFT5.0Progressed at 6 mos, recurred at 4 yrs
Mariniello et al., 201267/MC4–7IDEMGTRSFT1.0Disease free
75/FT6–7IDEMGTRSFT1.0Disease free
Wu et al., 201250/FL-2IDEMGTRSFTNRNRArising from filum terminale
Chen et al., 201243/MT11–12NRGTRSFT14.7Recurred at 14.7 yrs
63/ML4–S2NRGTRSFT2.8Disease free
Brigui et al., 201356/MT6–7IDEMGTRSFT2.4Disease free
Brigui et al., 201369/MT7–8EDGTR + preop emboMalignant SFT4.0Deceased from metastatic diseasePrimary pulmonary lesions; developed kidney/extremity/visceral mets
Montano et al., 201356/FL1–2IDEMGTRSFT1.0Disease free
Son et al., 201354/FT-8, S1–2EDSTR + preop embo + postop radiation/chemoMalignant SFT0.5Deceased from metastatic diseasePresented w/ multifocal disease (skull, spine, pelvis)
Tomek et al., 201366/MT11–12EDSTRSFT w/ retiform & papillary features4.1Progressed at 18 mos
Hwang et al., 201448/MC7–T1IDEMSTRSFT0.5No progression
Kobayashi et al., 201440/MC4–5IDEM & IDIMSTRSFT21.0Progression at 21 yrs
Nagano et al., 201457/FL4–5EDGTR + fusion (2 stages)Malignant SFT0.8Deceased from metastatic diseaseLocal & metastatic recurrence at 3 mos
Robert et al., 201449/FT9–10IDEM & IDIMSTRSFT0.5No progression
Sebaaly et al., 201432/FL3–4IDEMGTRSFT1.3Disease free
Tsutsumi et al., 201419/MC-1EDGTR + intraop embo + fusionSFT1.0Disease freePrimarily bone, had parapharyngeal lesion 10 yrs prior
Yuan et al., 201448/MT-9ED & IDEMGTRSFTNRNRDumbbell tumor
Basaran et al., 201567/ML-3IDEMGTRSFT1.0Disease free
Bruder et al., 201583/FT8–9IDIMGTR (2 stages)SFT0.7Disease free
Sade et al., 201543/MThoracicIDEMSurgerySFTNRNR
Walker et al., 201547/FL-1IDIMGTR + preop emboSFT0.5Disease freeHemorrhagic lesion in conus medullaris
Lavrador et al., 201523/FT11–12EDGTR + preop emboSFT0.5Disease freePrimarily extraspinal, dumbbell
Zaldivar-Jolissaint et al., 201633/MC1–4EDGTRSFT7.0Disease free
Present case10/MC1–3IDEMGTRSFT w/ atypical features1.0Disease free

Chemo = chemotherapy; ED = extradural; embo = embolization; FU = follow-up; IDEM = intradural extramedullary; IDIM = intradural intramedullary; mets = metastasis; NR = not reported; O = occiput.

Seventy-eight cases reported age at presentation. The majority of these cases occurred in adults (94.8% in patients over the age of 21 years). Patients ranged in age from 10 years (our patient) to 83 years (median 51.5 years). Seventy-eight cases contained information on patient sex. There is a slight male predominance in the reported cases of spinal SFT (56.4% male vs 43.6% female; Table 2).

TABLE 2.

Demographics and tumor characteristics

VariableValue
Age (yrs)
  Mean (SD)49.8 (15.4)
  Median (range)51.5 (10–83)
Sex
  Male44 (56.4%)
  Female34 (43.6%)
Level
  Occipitocervical2 (2.6%)
  Cervical21 (27.6%)
  Cervicothoracic3 (3.9%)
  Thoracic32 (42.1%)
  Thoracolumbar1 (1.3%)
  Lumbar11 (14.5%)
  Lumbosacral1 (1.3%)
  Sacral1 (1.3%)
  Multiple4 (5.3%)
Compartment
  Extradural18 (26.5%)
  Extradural & intradural extramedullary5 (7.4%)
  Intradural extramedullary24 (35.3%)
  Intradural extramedullary & intramedullary11 (16.2%)
  Intramedullary10 (14.7%)

Seventy-six reported cases indicated spinal level. The plurality of lesions occurred in the thoracic region (42.1%), followed by the cervical region (27.6%) and lumbar region (13.2%). The remaining tumors occurred in the sacrum,50 across junctional levels,1,11,13,22,28,46 or at multiple levels.35,47,67,68 Sixty-eight reported cases contained information on the spinal compartment involved. The plurality (35.3%) was intradural extramedullary, followed by extradural (26.5%). Of these extradural tumors, 6 were primarily extraspinal or bone as opposed to primarily intraconal (Table 2).27,31,40,51–53

Sixty-one reported cases contained information on MRI appearance. Tumors in all of these cases exhibited some degree of enhancement with intravenous contrast, most of them homogeneously enhancing. Most of the lesions were either hypointense or isointense on T1- and T2-weighted imaging, although rare tumors were hyperintense on one or the other of these sequences. A few reports indicated preoperative diagnoses, most often meningioma or nerve sheath tumor.2,10,43,64,65,72,73 One hemorrhagic lesion in the conus was thought to be either a myxopapillary ependymoma or cavernous malformation.74

Seventy-five of the reported cases contained information regarding treatment. Patients in all of these cases underwent surgery. Gross-total resection was achieved in 82.7% of patients, and subtotal resection (STR) was performed in 17.3%. Four patients (3 GTR and 1 STR) underwent preoperative embolization of the tumor.9,40,53,67 One GTR patient also underwent intraoperative embolization.71 Two of the GTR outcomes were achieved in 2 stages of surgery.10,51 Four patients (3 GTR and 1 STR) required spinal fusion at the initial presentation.26,31,51,71 A single patient with a malignant SFT was treated with chemotherapy and radiation after STR.67 Otherwise, chemotherapy and radiation were reserved for recurrences and/or metastases.9,26,46,50,51

Forty-seven patients had reports of intraoperative assessments of tumor origin. In most cases, the origin was either the spinal cord or the dura mater, with fewer reports of tumors arising from nerve roots. Four patients, including our own, had attachment to the pia mater.3,9,29 Four patients had tumors arising from bone or periosteum,26,52,67,71 2 patients had tumors involving the arachnoid,10,22 1 patient's tumor seemed to arise from the venous plexus.27

Seventy-eight cases indicated tumor histopathology. Sixty-nine patients (92%) had SFT without mention of malignant or other unusual features on pathology. Five patients (6.7%) had malignant SFT.9,24,35,51,67 Three of the previously reported cases included unusual pathological findings such as retiform or papillary features,70 focal pleomorphism,7 and lipomatous features.1 Our patient's tumor demonstrated atypical features without reaching the criteria for malignant SFT.

Outcome depended largely on histology and extent of resection. Four of the patients with malignant SFT had outcome data reported. All 4 died of their disease, one at 2 months,24 one at 6 months,67 one at 9 months,51 and one at 4 years.9 Fifty-six patients with SFT had outcome data reported. Follow-up times ranged from 2 months to 21 years. Twenty-two patients had follow-up of 1 year or less, and 45 patients had follow-up of 5 years or less. Outcome of SFT without malignant features seemed to depend largely on extent of resection. Nine SFT patients with STR had information on outcome. Three of these patients had only 6 months of follow-up and no recurrence or progression.28,34,62 Of the remaining 6 patients, 5 exhibited local disease progression between 6 months and 21 years after the first presentation.8,12,26,37,46 The final patient developed a new spinal lesion 14 years after the original surgery.56 Forty-six patients treated with GTR had data on outcome and recurrence. Of these patients, 41 (89.1%) had no recurrence at a median of 1.2 years of follow-up (range 2 months–7 years). One of these patients had residual disease elsewhere but no recurrence of the resected lesion.68 Three patients had single local recurrences at 2 years,22 8.5 years,46 and 14.5 years.14 Another patient developed local recurrences twice, once at 5 years and again at 9 years.25 The final patient developed malignant transformation of his tumor with pulmonary metastases at 3.5 years and local spinal recurrence and recurrent pulmonary and hepatic metastases at 5.5 years.50

Discussion

Solitary fibrous tumors are lesions of mesenchymal origin that differentiate primarily along fibroblastic lines. Characteristically, they demonstrate spindle cells in a collagen background. They are now thought to exist along a spectrum with hemangiopericytomas, representing a more cellular and vascular subtype of the same tumor category. The majority of SFTs exhibit benign histology and behavior; however, malignancy does occur and is evidenced by a high mitotic count, increased cellularity, hemorrhage and/or necrosis, pleomorphic nuclei, and foci of dedifferentiation.18

A borderline increase in the mitotic rate and a high proliferation index indicate atypical features of the SFT in our patient. Malignancy in SFT is not well described, and the criteria are mainly developed for the other end of the spectrum, that is, hemangiopericytoma.23,44 Nonetheless, a large series on soft tissue and pleural SFTs showed that patients 55 years of age or older with tumors 15 cm or larger and with a mitotic count of 4 or more per 10 hpf had a high risk of metastasis and death,18 while a proliferation index of 10% or more was found to be associated with malignancy in another study.6 The importance of the proliferation index has been emphasized in predicting prognosis in a series of CNS SFTs,14 as well as in a meta-analysis of CNS SFTs.5 Authors of the latter study concluded that a proliferation index of 5% or more may indicate a higher likelihood of recurrence.5

Solitary fibrous tumor was first described as a tumor arising from the pleura in the thoracic cavity. In this location, the majority of these tumors are benign. However, 10%–20% will exhibit locally aggressive behavior or malignancy. Surgery is the preferred method of treatment and carries with it a 5-year survival of close to 100%. Adjuvant therapy is reserved for metastatic or recurrent disease. Chemotherapy and radiation are only moderately effective. In the thorax, most tumors that recur do so within 2 years, and imaging is recommended every 6 months for 2 years followed by annual imaging. Malignant SFT carries a poor prognosis, with 63% of tumors recurring despite GTR and most patients dying within 2 years of diagnosis.15

A recent single-center review of 82 patients with SFT demonstrated a slight female predominance (57%).19 Among this study cohort there was a nearly even split between benign and malignant histologies. However, patients were identified through a search of a sarcoma database at a tertiary care cancer center that likely skewed the series toward a malignant profile. The median survival of patents with benign tumors was 15.5 years with a 5-year survival of just over 75%. The median survival of patients with malignant tumors was 7.8 years with a 5-year overall survival of 55%. While some patients with a benign histology did receive chemotherapy and radiation, these modalities were mostly reserved for patients with malignant SFT.

The literature on spinal SFT is limited to case reports and small case series. Therefore, we cannot comment on its incidence, although it does appear to be a very rare diagnosis. Likewise, since existing reports include very small numbers of patients, it is difficult to determine epidemiology, ideal treatment, follow-up, and overall prognosis. However, based on our review of 82 patients, we can attempt to draw some conclusions.

Not surprisingly, most of the tumors occur in the thoracic spine, as is seen with other spine neoplasms. The intradural extramedullary compartment of the spine is the most common space to find these tumors, although they are also frequently reported in the extradural space and intramedullary space with an exophytic component. Imaging characteristics, particularly for extradural and intradural extramedullary tumors, tend to mimic meningiomas and/or nerve sheath tumors. The tumors can arise from any tissue, and their origin is not always evident on imaging or during surgery.

With regard to management, the overwhelming majority of patients are treated with surgery. Gross-total resection should be the goal and can be curative. Subtotally resected tumors tend to recur, although the number of patients who underwent STR in our series is small. There does not appear to be a role for adjuvant therapy for the benign SFT patient who has had a successful GTR. Adjuvant therapy for residual benign SFT is probably also of little benefit given the overall good prognosis of these tumors and the literature on SFTs in other locations suggesting that adjuvant therapy is of little value for benign SFT. Malignant SFT, on the other hand, appears to have a very poor prognosis regardless of intervention. There were very few malignant SFT cases in our series, but the patients in these cases all fared poorly. In these patients, strong consideration should be given to resection followed by adjuvant therapy, although it is not clear how much impact this will have on life expectancy.

Despite its benign histology, SFT can recur. This has been seen with SFTs in other nonspinal locations. Most patients in our series had very short follow-ups. Interestingly, the tumors that did recur seemed to do so late (2 years, 8.5 years, 5 and 9 years, and 14.5 years), suggesting that there may be value in the long-term follow-up of patients. In addition, 3 of the patients with spinal SFT had prior intracranial lesions and presented with spinal lesions consistent with drop metastases. All of these lesions had benign histologies. The lag time between intracranial disease and the diagnosis of spinal disease was 10 years,68 14 years,56 and 15 years.47

Solitary fibrous tumors in any location are much more common in adults than in children. In the pleura, it seems that less than 2% of SFTs occur in children. In addition, children have a lower incidence of malignant pleural SFT than adults do.45 Solitary fibrous tumors have been reported in other locations in children including the mesentery,75 scalp,61 kidney,77 orbit,41 shoulder,60 and brain.63 Prior to this report, the youngest reported patient with spinal SFT was 17 years of age30 and only 2 other reported patients were younger than 21 years of age.11,71 Our patient is the first documented preadolescent child with spinal SFT.

The major limitation of this paper is its reliance on previously published case reports and case series. These previous reports have all been selected for publication based on unusual features of the cases. There is inevitably publication bias that introduces selection bias to this report. In addition, previous authors have been selective about the information they have included in their reports. Unfortunately, given the rarity of SFTs of the spine, larger studies are unlikely to be performed.

Conclusions

Solitary fibrous tumors of the spine are rare neoplasms. No large series exist. However, given this review of reported cases, it appears that the majority of these lesions are benign and should be treated with GTR alone. Even under these circumstances, however, the tumors can recur and thus long-term follow-up should be considered.

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Disclosures

The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

Author Contributions

Conception and design: Albert. Acquisition of data: both authors. Analysis and interpretation of data: Albert. Drafting the article: Albert. Critically revising the article: both authors. Reviewed submitted version of manuscript: Albert. Approved the final version of the manuscript on behalf of both authors: Albert. Statistical analysis: Albert. Study supervision: Albert.

  • View in gallery

    Preoperative axial T2-weighted MR image (A) demonstrating hypointensity of the lesion and cord compression. Preoperative sagittal (B) and coronal (C) T1-weighted MR images with contrast demonstrating homogeneous enhancement of the tumor. Postoperative coronal T1-weighted MR image (D) with contrast demonstrating GTR and reexpansion of the spinal cord.

  • View in gallery

    Intraoperative photographs of tumor resection. A: Initial view of tumor with dorsal nerve roots overlying the lesion. B: Pial attachment at caudal end of tumor. C: Attachment of tumor to pia of spinal cord. D: Tumor has been completely resected. Figure is available in color online only.

  • View in gallery

    Postoperative flexion (A) and extension (B) cervical spine radiographs demonstrating no evidence of dynamic instability.

  • View in gallery

    Microscopic findings. A: Low-power view with peculiar, well-defined, branching blood vessels (asterisk) and alternating dark and light areas reflecting variable cellularity and collagen. B: Spindle cell morphology of the neoplastic cells and mitotic activity (arrow). C: Thick, keloid-like collagen bundles and decreased cellularity in some areas. D: Diffuse and strong CD34 positivity. E: Nuclear STAT6 expression. F: Higher-than-expected Ki-67 proliferation index. H & E (A–C), original magnifications ×40 (A), ×200 (B–C), ×100 (D–F). Figure is available in color online only.

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