Christopher S Hong

Eric Sauvageau

Norman L Lehman

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Case Report
A Pilocytic Astrocytoma Mimicking a Clinoidal Meningioma
Christopher S. Hong,1 Norman L. Lehman,2 and Eric Sauvageau1
1 Department of Neurological Surgery, The Ohio State University Wexner Medical Center, 410 W. 10th Avenue,
N1022 Doan Hall, Columbus, OH 43210, USA
2Department of Pathology, The Ohio State University Wexner Medical Center, 333 W. 10th Avenue,
4169 Graves Hall, Columbus, OH 43210, USA
Correspondence should be addressed to Eric Sauvageau; eric.sauvageau@osumc.edu
Received 25 December 2013; Accepted 25 February 2014; Published 13 March 2014
Academic Editors: C. Chaskis, T. Krings, M. Leonardi, and A. Spalice
Copyright © 2014 Christopher S. Hong et al. This is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly
cited.
Pilocytic astrocytomas andmeningiomas are benign, primary brain tumors thatmay involve the optic tract. Classically, the presence
of a dural “tail” sign may differentiate a meningioma from other intracranial lesions. In this report, we describe a mass with the
typical appearance of a clinoidal meningioma on magnetic resonance imaging (MRI) but postoperatively diagnosed as a pilocytic
astrocytoma. This case illustrates the rare occurrence of a pilocytic astrocytoma mimicking a meningioma on MRI.
1. Background
Pilocytic astrocytomas are benign, World Health Organiza-
tion (WHO) grade I gliomas that most frequently arise in
adolescents and young adults and usually involve the cere-
bellum, hypothalamus, and optic pathways. Radiographically,
they are relatively well demarcated and strongly enhance
on MRI as they are well vascularized and often exhibit
glomeruloid vascular proliferation. Although rare, pilocytic
astrocytomas can originate from the optic pathway, anterior
or posterior to the optic chiasm. These lesions have a strong
association with neurofibromatosis type 1 (NF1) and are
estimated to occur in 15% of all patients with this inherited
syndrome [1].
In contrast, meningiomas are benign growths of arach-
noid cap cells, usually found at sites of dural reflections
within the skull, and classically exhibit a homogenously
enhancing thickening of the dural margin with peripheral
tapering on MRI, known as the “tail” sign [2]. Because of
these characteristic features, meningiomas are usually readily
identified based on clinical and radiographic findings alone,
often precluding a need for tissue biopsy prior to treatment.
In this case report, we describe a young patient whose
clinical and radiographic presentation strongly supported a
diagnosis of a meningioma but upon neurosurgical interven-
tion was found to have a pilocytic astrocytoma. We describe
the clinical course of our patient and highlight the unusual
features that were subsequently found.
2. Case Report
An 18-year-old female, 36 weeks into pregnancy, presented
to ophthalmology with poor right-sided vision evolving over
few years. Her exam was notable for right optic nerve pallor
and atrophy. A brain MRI without contrast due to her
pregnancy showed a right supraclinoid mass measuring 2.5
× 2.2 × 2.5 cm, for which she was referred for neurosurgical
evaluation. No other neurological deficits were present on
examination. Considering the stability of the visual deficit
and the late gestational age, a contrast study was postponed
until after her delivery. The subsequent MRI confirmed an
extra-axial mass in the right clinoid region with homogenous
enhancement and interval growth of the lesion to 2.9 × 3.0
× 2.0 cm (Figure 1). There were mild mass effect upon the
right aspect of the optic chiasm, evidence of a dural tail,
encasement of the right internal carotid artery, and possible
extension into the right cavernous sinus. Collectively, these
findings radiologically suggested a diagnosis of a right cli-
noidal meningioma.
The patient subsequently underwent surgical resection
via a right frontotemporal craniotomy. Intraoperatively, the
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Case Reports in Radiology
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http://dx.doi.org/10.1155/2014/524574
2 Case Reports in Radiology
(a) (b) (c)
Figure 1: (a) Axial, (b) coronal, and (c) sagittal T1-weighted MRI showing a homogenously enhancing lesion, measuring 2.9 × 3.0 × 2.0 cm
in the right clinoidal region. There is probable extension into the right optic canal, sphenoid sinus, right temporal fossa, and possibly right
cavernous sinus, suggestive of a right clinoidal meningioma.
(a) (b)
Figure 2: (a)The tumor consists of piloid cells and shows abundantmucin andRosenthal fibers (upper left) (H&E stain; originalmagnification
200x). (b) A few perivascular pseudorosettes were noted, here in longitudinal section (H&E stain; original magnification 200x).
frontal excursion of the tumor had a well-defined arachnoid
plane, but further opening of the dura revealed tumor infil-
tration of the optic nerve, whichwas unexpected for amenin-
gioma.A biopsywas taken from the superior truncal aspect of
the tumor and sent to pathology for intraoperative diagnosis,
which returned a diagnosis of pilocytic astrocytoma. The
final pathology report described a proliferation of piloid glial
cells of low to moderate cellularity associated with abundant
Rosenthal fibers, rare eosinophilic granular bodies, and
microvascular proliferationmostly located at the periphery of
the tumor (Figure 2). A few pilomyxoid features were noted,
including abundant extracellular mucin, some perivascular
pseudorosetting, and paucity of eosinophilic granular bodies.
Collectively, the histologic findings confirmed a diagnosis of
pilocytic astrocytoma, WHO grade I.
Postoperatively, the patient recovered without signifi-
cant complications and reported improved overall vision at
her one-month follow-up visit. The 6-month postoperative
MRI showed no interval growth of the residual tumor,
and the patient is currently receiving regular surveillance
imaging.
3. Discussion
Numerous factors led us to initially believe that our patient’s
lesion was dural based. Radiographically, the MRI showed
a uniformly enhancing lesion that seemed to communicate
with the dural surface overlying the right clinoidal area.
While there seemed to be extension into the optic canal,
preoperative imaging did not suggest optic nerve infiltration.
Clinically, our patient had no features of NF1 to support a
tumor originating from the optic nerve. Furthermore, the
accelerated interval growth of her lesion during pregnancy
was consistent with known effects of gestational hormones
on meningioma proliferation [3]. Intraoperatively, however,
there were clear involvement and possibly origination of the
tumor from the optic nerve, given the preserved arachnoid
plane along its borders, which supported the final pathologic
diagnosis of an astrocytoma.
A thorough review of the literature revealed only one
other report of an optic pathway gliomamimicking a menin-
gioma on preoperative imaging. Edwards et al. recently dis-
cussed a case of an 11-year-old child who presented with com-
plaints of right-sided vision loss. On preoperative imaging,
Case Reports in Radiology 3
there were an enlarged right optic nerve and a homogenously
enhancing, dural-based lesion that extended into the right
temporal lobe [4]. During surgery, however, it was clear that
the tumor involved white matter tracts, most likely derived
from the right temporal lobe. Notably, while hyperintensity
on T2-weighted MRI suggested infiltration into the optic
tracts, this could not be visualized, intraoperatively. The final
histologic diagnosis was a pilomyxoid astrocytoma.
Pilomyxoid astrocytomas were first described in 1999 and
subsequently were recognized by theWHO in 2007 as amore
aggressive, histological variant of pilocytic astrocytomas. On
MRI, these tumors usually enhance homogenously within
the chiasmatic-hypothalamic region. Unlike pilocytic astro-
cytomas, they exhibit T2 signal extension into surrounding
deep white and grey matter, in contrast to our patient’s radio-
graphic presentation. Interestingly however, the pathology of
our biopsy sample did report limited pilomyxoid features.
Generally, less than 5% of pilocytic astrocytomas progress
towards malignancy [5]. Still, our patient will continue to be
closely monitored for signs of disease progression.
4. Conclusion
In this case report, we describe the clinical course of a
patient who presented with clinical and radiographic signs,
all suggestive of clinoidal meningioma. However, the gross
appearance and histology of the lesion demonstrated a
pilocytic astrocytoma. Therefore, physicians should consider
a pilocytic astrocytoma in their differential diagnosis of
any dural-based, enhancing lesion within the periclinoidal
region.
Conflict of Interests
The authors declare that there is no conflict of interests
regarding the publication of this paper.
References
[1] R. Listernick, J. Charrow, M. Greenwald, andM.Mets, “Natural
history of optic pathway tumors in children with neurofibro-
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[2] S. T. Qi, Y. Lui, J. Pan et al., “A radiopathological classification
of dural tail sign of meningiomas,” Journal of Neurosurgery, vol.
117, no. 4, pp. 645–653, 2012.
[3] E. A. Lusis, B.W. Scheithauer, A. T. Yachnis et al., “Meningiomas
in pregnancy: a clinicopathological study of 17 cases,” Neuro-
surgery, vol. 71, no. 5, pp. 951–961, 2012.
[4] J. R. Edwards, C. G. Kulwin, S. E. Martin et al., “Temporal
and optic pathway pilomyxoid astrocytoma mimicking dural-
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[5] P. B. Dirks, V. Jay, L. E. Becker et al., “Development of
anaplastic changes in low-grade astrocytomas of childhood,”
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Case Report A Pilocytic Astrocytoma Mimicking a Clinoidal Meningioma

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Case Report A Pilocytic Astrocytoma Mimicking a Clinoidal Meningioma

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