Giant Intraosseous Cellular Schwannoma of the Sacro

Case Report
eISSN2465-891X The Nerve.2016.02(1):13-15
http://dx.doi.org/10.21129/nerve.2016.2.1.13
www.thenerve.net
Giant Intraosseous Cellular Schwannoma of the Sacro-pelvic
Region in a Young Woman
Seon Woong Choi1, Sang Uk Kim2, Young Woo Kim1, Seong Rim Kim1,
1
1
Sang Don Kim , Ik Sung Park
1
Department of Neurosurgery, Bucheon St Mary’s Hospital, The Catholic University of Korea College of Medicine, Bucheon,
Department of Neurosurgery, St. Vincent Hospital, The Catholic University of Korea College of Medicine, Suwon, Korea
2
Giant intraosseous schwannoma is very rare. Schwannomas arising around the sacrum can reach a considerable size before
becoming symptomatic because of their insidious and slow growth, which can allow the displacement of nerves and internal
organs, often resulting in extensive bone erosion. The treatment of these giant schwannomas causes significant neurological
disability. A 29-year-old woman was suffering from paresthesia of her left posterior thigh. Her symptom was aggravated
since the last 5 months. Neurological examination showed paresthesia in the left S2 and S3 dermatome. There was no
anal sphincter dysfunction or voiding difficulty. Plain radiography demonstrated foraminal widening of the left S2. Pelvic computed tomography (CT) and magnetic resonance images (MRI) showed a huge mass extending from the sacrum (S2) to the
presacral area. The size of the lobulated mass was 4×4×6 cm. The patient underwent laminectomy and gross total removal
of the tumor. Through a posterior approach, the tumor was removed without any neural or visceral organ injury, including
the left S2 root. After a 71-month follow-up, the neurologic examination was normal, the urodynamic tests continued to show
no abnormal signs, and the MRI studies revealed no evidence of residual tumor or recurrence.
Key Words: NeurilemmomaㆍSacrumㆍSurgical procedures operativeㆍTreatment outcome
INTRODUCTION
Cellular schwannoma is a benign variant of Schwann cell
tumor, which is distinguished from classic schwannoma by
vigorous cellular growth and absence of Verocay bodies. White
et al.8) reported that the main sites of occurrence were the
intraspinal and paraspinal region in the mediastinum and the
retroperitoneum with the tumor sometimes occurring in the
sacrum. Intraosseous schwannoma was reported to account
for less than 0.2% of all bony tumors3), and sacral schwannoma
accounts for less than 1% to 5% of all spinal schwannomas.
Giant intraosseous schwannoma is very rare. The tumor often
affects middle-aged women. As reported previously, schwannomas arising around the sacrum can reach a considerable
size before becoming symptomatic because of their insidious
and slow growth, which may allow the displacement of nerves
and internal organs, often resulting in extensive bone erosion5).
Corresponding author: Sang Uk Kim, MD, PhD
Department of Neurosurgery, St. Vincent Hospital, The Catholic University
of Korea College of Medicine, 93-1, Jungbu-daero Paldal-gu, Suwon-si,
Gyeonggi-do 16247, Korea
Tel: +82-31-249-8163, Fax: +82-31-245-5208
E-mail: [email protected]
The treatment of these giant schwannomas causes significant
neurological disability. In this paper, we showed that detailed
preoperative planning, careful dissection and sparing of uninvolved nerve roots made it possible to prevent unnecessary
neurological impairment.
CASE REPORT
A 29-year old woman was suffering from paresthesia of
her left posterior thigh. Her symptom was aggravated since
the last 5 months. Neurological examination showed paresthesia in the left S2 and S3 dermatome. There was no anal
sphincter dysfunction or voiding difficulty.
Plain radiography demonstrated foraminal widening of the
left S2. Pelvic computed tomography (CT) and magnetic resonance images (MRI) showed a huge mass extending from the
sacrum (S2) to the pre-sacral area. The size of the lobulated
mass was 4×4×6 cm and it was located above the anteflexed
uterine corpus.
For planning of this surgical procedure, three-dimensional
CT (3D CT) and MRI were beneficial in determining the extension and the nature of the tumor, but a digital subtraction
angiography (DSA) study was not performed.
Journal of the Korean Society of Peripheral Nervous System
13
Giant Intraosseous Cellular Schwannoma of the Sacro-pelvic Region in a Young Woman
DISCUSSION
7)
Fig. 1. Preoperative contrast-enhanced axial (A), sagittal (B) Magnetic resonance images revealing a 4×4×6 cm sized huge schwannoma.
Fig. 2. Preoperative plain radiograph demonstrated a widened
foramen of S2 (A) Pelvic computed tomography also showed a
presacral mass (B).
Fig. 3. Postoperative enhanced magnetic resonance images showing that the gross total mass was removed (A) and photomicrographs obtained during histological analysis. Staining of the tumor
(B) (H&E, original magnification ×60).
Through a linear shaped, sacral posteromedial incision, supplementary bone demolition, which is left hemilaminectomy
of the sacrum, was performed. After a T-shaped dural incision
was made, a whitish-yellow mass was noted under the dorsal
root S2. The lesion was microsurgically debulked and removed.
Via this posterior approach, we removed the tumor totally
without any neural or visceral organ injury. Instrumental spondylodesis was not performed. Immediately after the procedure,
the patient had no neurological deficit. On the postoperative
radiographs, there was no sign of spinal instability. After a 71month follow-up, the neurologic examination was normal, the
urodynamic tests continued to show no abnormal signs, and
the MRI revealed no evidence of residual tumor or recurrence.
14 www.thenerve.net
Turk et al. reviewed 21 cases of giant intrasacral schwannoma among 79 cases of intraosseous schwannoma reported
in the English literature until 1992. They stated that a giant
intrasacral schwannoma was a rare retrorectal mass. Because
of slow tumor progression, the patients experienced pain and
swelling late during the development of the lesion. There have
been no reported cases of malignant intrasacral schwannomas.
However, it may be very likely for cellular schwannoma to
deceive us into the wrong diagnosis of malignant peripheral
nerve sheath tumor because of its remarkable growth and the
invasion of bony tissue5). Malignant peripheral nerve sheath
tumors of larger than 5 cm, especially those associated with
neurofibromatosis, were reported to adversely affect the prognosis4). Therefore, biopsy should be performed preoperatively
to establish a conclusive diagnosis8).
For the treatment of the tumor, total removal of the lesion
was considered curative, and adjuvant chemotherapy or radiation therapy was not worthy of being carried out5,7,8). Turk
et al.7) and White et al.8) emphasized that basically cellular
schwannoma was benign and that unnecessary sacrifice of intact nerves should be avoided on removal of the tumor.
While planning sacral amputation, the proximal involved
site in the sacrum may determine the level of sacral resection.
For performing sacral amputation, it is important to know the
resulting functional effects on the pelvic visceral organs and
to know if the strength of the remaining pelvic girdle is enough
for the normal load during activities of daily living10). Bilateral
preservation of the S1 nerve roots is necessary to preserve
the locomotor function of the lower extremities. Unilateral
S2 and S3 nerve root preservation is expected to retain satisfactory urinary and rectal function. Regarding the biomechanical strength of the pelvic girdle, Gunterberg et al.2) described that an amputation done through the S1 vertebral body
weakened the pelvic girdle by approximately 50% and an amputation between S1 and S2 weakened the posterior arch of
the pelvis by approximately one third. Taking the above points
into consideration, in our patient, high sacral amputation between S1 and S2 with marginal resection of the tumor and
release of the left S2 and S3 nerve roots from the sacrum
were performed. These surgical options were possible thanks
to the development of a unique threadwire saw9). Furthermore,
the lumbar spine was connected to the pelvis with spinal instrumentation accompanied by posterolateral fusion. Through
a combined anterior and posterior approach, the large tumor
could be removed en bloc. Our case underwent one-stage operation, which is different from the other case reports in which
Choi SW et al.
the operation was done by using a two-stage approach. During
several months after surgery, the patient was bothered by difficulties with urination and defecation, but this impairment
gradually improved within 7 months postoperatively. There
were no signs of recurrence of the tumor. The clinical results
indicated that the long time taken for the operation was worth
it for achieving a satisfactory functional outcome, and cautious
nerve root-sparing dissection may be the most important factor to lessen postoperative neurologic deficits.
Patients who have a large presacral schwannoma without
any neurologic impairment, and no evidence for the tumor
to change its size on imaging studies may not be candidates
for a high sacral amputation because of the great possibility
of sacrificing sphincter function or creating dreadful neurologic deficits intraoperatively. Another treatment option may
be to simply observe the patients at the present moment.
However, it must be kept in mind that the tumors have a
potential to imperil bladder and bowel function and destroy
the connection between the lumbar spine and pelvic arch if
left untreated. Because the symptomatic recurrence after debulking or decompression by piecemeal dissection was reported to be very high in giant intrasacral schwannomas1,7),
complete tumor resection will be able to yield enough content
with the treatment to the patients eventually.
Preoperative imaging studies including radiographic films,
CT (especially 3D CT), and MRI were beneficial in determining the extension and the nature of the tumor and are mandatory for planning the surgical treatment6). CT or MRI demonstrated well the association of the tumor to the neighboring
visceral organs such as the rectum and the bladder. The preoperative angiographic study was valuable in identifying the
arteries that fed the tumor. Although the tumor showed hypovascularity on the angiograms, fortunately embolization with
coils done the day before surgery was useful to reduce blood
loss because the arteries were undetectable and it was hard
to secure hemostasis because the tumor occupied the entire
cavity of the pelvis.
CONCLUSION
A case of intrasacral cellular schwannoma with one of the
largest volumes previously described in the literature was reported. High sacral amputation after a combined anterior and
posterior approach could be performed without causing any
disability. Detailed preoperative planning, careful dissection and
sparing of uninvolved nerve roots made it possible to prevent
unnecessary neurologic impairment.
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