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International Journal of Clinical Case Reports
2
department with the diagnosis of possible lumbar disc
herniation. On examination, she presented with a very
obvious left foot drop. Straight leg raising test was 40
degrees for the left leg. There was marked weakness
along the L5 and S1 distribution with significant
sensory impairment as well as decreased ankle reflex.
There was a slight weakness in the L4 muscle
innervation as well. However, further MRI scan of the
spine did not show any herniation of the disc or
external compression of the nerve.
Convinced that it was a sciatica nerve compression, a
subsequent MRI of the pelvis was performed. It
revealed a large soft tissue mass at the centre of the
left buttock which arise from the sciatica nerve at the
level of the great sciatic notch. It measured 10.8 cm
(supero- inferiorly) × 9.6 cm (transversely) × 7.8 cm
(antero-posteriorly). There was no evidence of local
invasion into the surrounding tissues. Staging CT scan
did not reveal any metastasis of the tumour. Genetic
testing was also performed and she did not carry
Neurofibromatosis 1 gene.
The biopsy result revealed malignant peripheral nerve
sheath tumour (MPNST). The patient underwent a
complete resection of tumour with clear margins of
the tumour. She was recovering well from the
operation without any complications and was
commenced on chemotherapy. A vigilance MRI
examination was performed 5 months post-operatively
with no evidence suggesting of local recurrences.
However, patient started being breathless and lethargic.
A surveillance CT scan was performed which revealed
presence of multiple well defined pulmonary
metastasis and a 14 mm subcutaneous nodule in the
right anterior abdominal wall.
2 Discussion
Malignant Peripheral Nerve Sheath Tumour (MPNST)
is an extremely rare medical condition with an
incidence of 1 in every 100 000 population (Karr et al.,
2006). It is a heterogenous group of tumour arising
from the Schwann cells or the perineural cells
(Omezzine et al., 2009). It accounts for 3%~10% of
all soft tissue sarcoma (Katz et al., 2009). Almost half
of the MPNST are associated with Type 1
Neurofibromatosis or von-recklinghausen’s disease,
an autosomal dominant disease which is associated
with inactivation of NF1 gene (Omezzine et al., 2009;
Katz et al., 2009; Dimou et al., 2009). It can also be
associated with post-radiation. The rest of the
incidences are sporadic causes. It is more common
between the age group of 20 to 50 years old, with a
predisposition to the 4
th
decade of life (Lin et al.,
2007). In patients with neurofibromatosis, the disease
will manifest earlier by at least one decade (Geller and
Gebhardt, 2006). The mean age for the presentation of
the disease in sporadic cases is 39.7 as compared to
those with neurofibromatosis with mean age of 28.7
(Karr et al., 2006; Nthumba and Juma, 2011). MPNST
can also occur in children with NF-1 mutation (Dimou
et al., 2009; Geller and Gebhardt, 2006).
The common site of presentation is usually at the large
nerve trunk in the peroneal nerve, sciatica nerve,
radial plexus and sacral plexus (Nthumba and Juma,
2011; Geller and Gebhardt, 2006). In patients with
neurofibromatosis, it usually develops from deep
seated plexiform neurofibroma. It presents with
symptoms of nerve compression such as paraesthesia,
radicular pain and weakness (Nthumba and Juma,
2011; Rodero et al., 2004). Hence, clinically it is very
difficult to differentiate sciatica caused by spinal
pathology from MPNST at the proximal sciatic nerve.
However, our case report revealed that the patient has
been suffering from sciatica for 15 months without
complaining of a mass until a later stage. Given the
history of trauma accompanied by proximal sciatica
and foot drop, it is not uncommon to misdiagnose it as
traumatic neuropathy or spinal cause of sciatica.
It has a poor prognosis with a 5 year survival rate
stands between 20%~50% (Katz et al., 2009). It is
biologically aggressive and has a very high propensity
to metastasise. The local recurrence rate and
metastatic rate after a complete surgical excision
ranges from 40% to 65% and 40% to 68%
respectively (Geller and Gebhardt, 2006).
MRI is the preferred radiographic method as part of
the integral management of MPNST (Wasa et al.,
2010). It is very useful in differentiating between
benign and malignant peripheral nerve sheath tumour,
especially deep seated sarcoma where dissemination
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