- Department of Neurosurgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
- Department of Neuropathology, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
Department of Neurosurgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
DOI:10.4103/2152-7806.98518Copyright: © 2012 Kikkawa Y. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
How to cite this article: Kikkawa Y, Nakamizo A, Suzuki SO, Tanaka S, Tsuchimochi R, Amano T, Yoshimoto K, Mizoguchi M, Iwaki T, Sasaki T. Spinal endodermal cyst resembling an arachnoid cyst in appearance: Pitfalls in intraoperative diagnosis of cystic lesions. Surg Neurol Int 14-Jul-2012;3:78
How to cite this URL: Kikkawa Y, Nakamizo A, Suzuki SO, Tanaka S, Tsuchimochi R, Amano T, Yoshimoto K, Mizoguchi M, Iwaki T, Sasaki T. Spinal endodermal cyst resembling an arachnoid cyst in appearance: Pitfalls in intraoperative diagnosis of cystic lesions. Surg Neurol Int 14-Jul-2012;3:78. Available from: http://sni.wpengine.com/surgicalint_articles/spinal-endodermal-cyst-resembling-an-arachnoid-cyst-in-appearance-pitfalls-in-intraoperative-diagnosis-of-cystic-lesions/
Background:Surgical treatment of endodermal cysts requires total removal of the cyst wall during the first operation to prevent recurrence. Therefore, intraoperative pathological diagnosis plays an important role in determining the optimal surgical strategy. We present a rare case of a spinal endodermal cyst and discuss its diagnostic difficulty during the intraoperative pathological examination.
Case Description:An 18-year-old male presented with progressive paraparesis and precordial oppression. Magnetic resonance (MR) imaging revealed an intradural extramedullary cystic mass having the same signal intensity as cerebrospinal fluid (CSF) without gadolinium enhancement at the T1-T2 level. The preoperative diagnosis was an endodermal or arachnoid cyst. The patient underwent surgery. An intraoperative frozen section showed a cyst wall consisting of loose, thin, fibrous tissue intermittently covered by flattened epithelium. The diagnosis was an arachnoid cyst. Accordingly, partial resection of the cyst wall was performed to create CSF communication between the cyst and subarachnoid space. However, the postoperative pathological diagnosis from permanent sections was an endodermal cyst, which was lined with ciliated columnar epithelium that was immunopositive for cytokeratin and epithelial membrane antigen. Subsequent paraffin embedding and immunostaining of the intraoperative frozen sample also confirmed patchy cytokeratin expression by all flattened epithelial cells. The patient's cyst had refilled 10 months after surgery, and he subsequently underwent fenestration of the cyst wall and placement of a cyst-subarachnoid shunt.
Conclusion:Examination of multiple samples from multiple sites or intraoperative immunostaining of frozen sections is recommended for accurate intraoperative diagnosis of endodermal cysts.
Keywords: Intradural spinal cyst, endodermal cyst, arachnoid cyst, intraoperative pathological diagnosis, cytokeratin
Endodermal cysts are rare, but well-known cystic lesions of the spinal canal that occur in the lower cervical and upper thoracic spine in particular.[
We report here a case of a spinal endodermal cyst that was diagnosed intraoperatively as an arachnoid cyst. We demonstrate detailed clinicopathological findings and discuss the difficulty in pre- and intraoperative diagnosis of spinal cystic lesions.
An 18-year-old male presented with a 1-month history of progressive weakness in the lower extremities and progressive precordial oppression. He had a three-year history of occasional precordial oppression. Neurological examination revealed mild symmetric paraparesis with grade 4+/5 strength on manual muscle testing and bilateral severe hypesthesia below the T4 level. The deep tendon reflex in the lower extremities was markedly increased, and Babinski's sign was observed bilaterally. He had difficulty with tandem gait. His peak urinary flow rate was moderately decreased. Magnetic resonance (MR) imaging of the thoracic spine revealed an intradural extramedullary cystic tumor at the T1-T2 level that was severely compressing the spinal cord from the ventral side [
Tumor removal was performed through a C7-T2 laminoplastic laminotomy. The spinal cord was bulging, but the cyst wall was not identified through the pia mater. After the spinal cord was longitudinally split along the posterior median sulcus, the cyst wall, which had a thin, translucent, membranous appearance, was identified at the ventral side of the flattened spinal cord through the split posterior median sulcus [
Eleven months after the first operation, fenestration of the cyst wall and insertion of a cyst-subarachnoid shunt were performed using the same approach as the first operation [
Intraoperative pathological examination of frozen sections revealed that the cyst wall was composed of a loose, thin, fibrous membrane containing melanocytes and was intermittently lined with flattened or partially cuboidal epithelial cells [Figure
Endodermal cysts occur most frequently in the spinal canal, mainly in the lower cervical and upper thoracic spine.[
Endodermal cysts are usually iso- to hypointense on T1-weighted MR images, iso- to hyperintense on T2-weighted MR images, and show no restriction of water diffusion on diffusion-weighted (DW) MR images.[
Considering the location and radiographic appearance of the lesion and the progressive clinical course of our patient, the cyst was preoperatively diagnosed as an endodermal cyst in the present case. However, the signal pattern of the cyst fluid was similar to the CSF on MR images, and so preoperatively, we could not completely rule out a spinal intradural arachnoid cyst. The therapeutic strategy for endodermal cysts is different from that for arachnoid cysts. For endodermal cysts, recurrence is frequent when the lesion is not completely removed. Total removal of the cyst wall is therefore recommended during the first surgery.[
In the present case, there was a discrepancy in the diagnosis between frozen sections and permanent paraffin sections. The findings in the intraoperative frozen specimen suggested an arachnoid membrane with mechanically deformed arachnoid cells due to the pressure of the cyst contents rather than an endodermal cyst because the cyst wall was composed of flattened epithelial cells with neither cilia nor discernible mucin production intermittently lining a loose, thin, fibrous tissue containing melanocytes. In addition, macroscopic observation during the operation also revealed that the cyst wall consisted of a thin, whitish, translucent membrane that was similar to the arachnoid membrane, and the cyst fluid was similar in appearance to the CSF. According to the intraoperative diagnosis, we performed a partial resection of the cyst wall to create communication between the cyst and the subarachnoid space. Subsequent paraffin embedding and immunohistochemistry of the intraoperative frozen sample confirmed that the epithelium was immunopositive for cytokeratin.
In general, cytokeratins are expressed specifically in epithelial cells. It has been reported that normal arachnoid cells do not express cytokeratin.[
For intraoperative frozen diagnosis of spinal cystic lesions, we recommend obtaining multiple frozen samples from multiple sites to help avoid misdiagnosis. In addition, rapid immunostaining of frozen sections within a tolerable time span during the operation is very helpful for obtaining an accurate diagnosis.[
In the present case, the extent of the cyst removal could not have been increased even with a correct intraoperative diagnosis because of the tight adhesion of the cyst wall to the spinal cord tissue. However, additional procedures such as placement of a cyst-subarachnoid shunt would have been attempted at the initial surgery if the correct intraoperative diagnosis had been made based on appropriate sampling, and this may have prevented subsequent refilling of the cyst and reoperation. We conclude that it is important to recognize the above-mentioned pitfalls and the options for examining tissue for intraoperative diagnosis of cystic lesions.
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