Posterior mediastinal ectopic meningioma: a case report
Lu et al. World Journal of Surgical Oncology
Posterior mediastinal ectopic meningioma: a case report
Chenying Lu 0
Xianghua Hu 0
Min Xu 0
Weibo Mao 1
Hongyuan Yang 0
Zufei Wang 0
Jiansong Ji 0
0 Department of Radiology, Lishui Hospital of Zhejiang University, Lishui Central Hospital, the Fifth Affiliated Hospital of Wenzhou Medical University , No. 289, Kuocang Rd., Lishui District 323000Zhejiang , China
1 Department of Pathology, Lishui Hospital of Zhejiang University, Lishui Central Hospital, the Fifth Affiliated Hospital of Wenzhou Medical University , No. 289, Kuocang Rd., Lishui District 323000Zhejiang , China
Primary ectopic meningiomas occurring in the mediastinal region are extremely rare. So far, only five cases of primary mediastinal meningioma have been reported in the literatures. The imaging characteristics and the clinicopathological significance of mediastinal psammomatous meningioma have not been detailed. Here, we report the case of a 42-year-old male with primary posterior mediastinal psammomatous meningioma. The clinical features, imaging, and pathological findings are carefully analyzed, and the relevant literatures were reviewed.
Mediastinum; Ectopic; Meningioma
Derived from the meningothelial cells capping the
arachniod villi, meningioma is a common neoplasm of the
central nervous system (CNS) . Most meningiomas
are located in the cranial cavity, in the vicinity of venous
sinus and attached to the dura. Occasionally, primary
meningiomas occur ectopically, for example, in the head
and neck region (orbit of the eye, nose, paranasal
sinuses, mandible, and ear) or paraspinal soft tissues [1-4].
Although exceedingly rare, primary ectopic
meningiomas have been reported to occur on the sites including
the foot, skin, retroperitoneum, and mediastinum
[2,5-7]. The rarity and uncertainty of etiology of primary
ectopic meningiomas at these sites may pose difficulties
for the correct diagnosis [6,7]. Here, we report the imaging
findings and the pathological manifestations of a rare case
of primary psammomatous meningioma that occurred in
the posterior mediastinal region. The contributions of
imaging and pathological examinations to the diagnosis and
differential diagnosis are discussed.
A 42-year-old Chinese male was admitted for a 6-year
history of dysphagia lusoria. His past medical history
was unremarkable. At admission, general conditions
were satisfactory, and a physical examination of the thorax
was normal. Routine laboratory tests were within normal
values, but a chest radiograph revealed a large mass with
calcification in the mediastinum. Esophagus barium
opacification showed that the middle and inferior segment of
the esophagus was compressed by the mass (Figure 1). A
computed tomography (CT) scan of the chest revealed the
presence of an ovoid mass about 4.8 7.6 10.0 cm in the
right posterior mediastinal region. The mass showed a
heterogeneous density accompanied with pronounced
calcification. Administration of contrast medium gave only a
mild strengthening of mass (Figure 2). A magnetic
resonance (MR) imaging showed a well-circumscribed mass
which was isointense-hypointense on T1-weighted
imaging and hypointense on T2-weighted imaging (Figure 3).
An enhanced MR imaging of the head and spine revealed
no abnormal findings. A diagnosis of teratoma was first
suggested. The tumor was then surgically removed through
a right thorax incision.
The patient underwent surgical resection of the
mediastinal tumor through the right thorax incision. During
the operation, the tumor was located in the posterior
mediastinum. It was found to have extended under the
bronchial bifurcation. Based on this surgical finding, the
mass was in close relationship with the esophagus and
pericardium; the esophagus was obviously compressed
and displaced. The tumor was a clearly demarcated
encapsulated solid mass with brown-gray color and
offwhite cut surface. After being routinely fixed with 10%
formaldehyde and embedded in paraffin, the tumor sample
Figure 1 A chest lateral radiograph shows a large mass with lots of calcification in the mediastinum; esophagus barium opacification shows that
the middle and inferior segment of the esophagus was compressed by the mass.
was processed, and 4-m-thick tissue sections were
obtained. The hematoxylin and eosin (H-E) staining (Figure 4)
showed that the tumor was composed predominantly of
bundles of elongated spindle-shaped cells with little oval
nuclei. There was heavy deposition of collagen fibers
between the tumor cells. In some areas, typical whorl
structure of mengingioma was observed. In addition,
multiple psammoma bodies were seen. There were no
mitotic figures and necrosis. Immunohistochemical
staining revealed that the tumor cells were positive for
epithelial membrane antigen (EMA) and vimentin, and
negative for CD34, bcl-2, SMA, and S-100 protein. The
Ki-67-labelling index was <5%. According to the
histological and immunohistochemical features, the tumor
was diagnosed as a benign mediastinal psammomatous
meningioma (World Health Organization (WHO)
grade I, based on the 2007 WHO classification ). At
follow-up 24 months after surgery, there was no
evidence of local recurrence or distal metastasis.
Meningiomas are usually clinically indolent and
morphologically heterogeneous tumors; they may exhibit a
variety of different histologic patterns [1,2]. Primary
ectopic meningiomas are very rare with the incidence
ranging from 0.9% to 2.0% of all meningiomas .
Their occurrence in the mediastinum is even rarer [6,7].
Their histopathogenesis is unclear. However, four
hypotheses of the formation of ectopic meningiomas have been
suggested: (1) direct extension of an intracranial lesion, (2)
distant metastasis from an intracranial meningioma, (3)
origination from arachnoid cells within the sheaths of
cranial nerves, and (4) origination from embryonic nests of
arachnoid cells .
Imaging features of ectopic meningioma are varied
among different histopathogenical types. Fibrous
meningioma, malignant meningioma, and angioblastic
meningioma located in the mediastinum had been reported
in the previous literature [6,7]. The case we report here
is a posterior mediastinal psammomatous meningioma
with characteristic imaging findings of calcification in
the tumor. Imaging findings show a well-defined mass
located in the posterior mediastinum with multiple
calcification foci, which obviously compresses the esophagus.
Dynamic CT only slightly enhanced the mass. These
imaging characteristics are similar to those of
intracranialand extracranial-originated calcified meningiomas [1,2].
The imaging differential diagnosis for a posterior
mediastinal mass containing calcification foci commonly includes
Castleman disease, teratoma, or neurogenic tumor [10-13].
Figure 2 Chest unenhanced CT scan shows a heterogeneous mass with calcification located in the posterior mediastinum. Its border was clearly
demarcated, and enhanced CT scan shows the mass with little enhancement.
Figure 3 Axial T1-weighted MRI shows a well-circumscribed isointense-hypointense mass located in the posterior mediastinum, and coronal
T2-weighted MRI shows a hypointense tumor located under the tracheal carina.
Figure 4 Hematoxylin and eosin (H-E) staining shows that the tumor is composed prominently of elongated spindle cells and collagen fibers;
numerous typical whorl formations and multiple psammoma bodies are observed in the tumor. Immunohistochemistry shows positive staining
for epithelial membrane antigen (EMA). (Magnification shown at 100).
Table 1 Immunohistochemical findings of different mesenchymal tumors
Meningioma [1-9,14] Solitary fibrous tumor  Leiomyoma  Hemangiopericytoma [14, 17] Neurogenic tumors 
EMA, epithelial membrane antigen; SMA, smooth muscle actin.
The mass of Castleman disease usually displays punctuate
or arborizing calcification with obvious strengthening on an
enhanced scan [10,11]. Teratoma often showed
heterogeneous densities within the mass caused by calcification
and fat tissues . Finally, the most common cause of a
posterior mediastinal mass, neurogenic tumors, are often
accompanied by cystic or hemorrhagic areas .
A definite diagnosis can only be made upon
histopathological and immunohistochemical findings. In this
case, H-E staining showed that the tumor is composed of
elongated spindle cells and collagen fibers, the common
features of meningioma [1-9]. The findings of typical
whorl formations and multiple psammoma bodies confirm
the diagnosis of psammomatous meningioma [1,2].
Immunohistochemistry is a powerful tool to differentiate
meningioma from other mesenchymal tumors, such as
solitary fibrous tumor, leiomyoma, hemangiopericytoma,
and neurogenic tumors. The immunohistochemical
staining features of these tumors are summarized in Table 1
[14-19]. The tumor cells in our report showed positive
staining for vimentin and EMA, which further support the
diagnosis of meningioma . Last, but not least, as there
was no clinical or radiological evidence of any intracranial
or intraspinal lesion, we concluded that the meningioma
in this case was of complete mediastinal origin.
In summary, primary meningioma of the posterior
mediastinum is extremely rare; they need to be differentiated
from other tumor masses. Radiological imaging is useful
in preoperative diagnosis and surgical planning, but the
ultimate diagnosis has to be confirmed by
Written informed consent was obtained from the patient
for publication of this case report and any accompanying
images. A copy of the written consent is available for
review by the Editor-in-Chief of this journal. This case
report was performed in compliance with the Helsinki
CL and XH collected all data and wrote the manuscript. MX and HY
prepared the radiological images. WM provided histopathologic
confirmation. ZFW and JSJ conceived of the concept and revised the
manuscript. All the authors read and approved the final version and agreed
to publish the manuscript.
This work was supported in part by grants from the Science and Technology
Support Key Program of Zhejiang (2013C03010) and the Public Welfare
Technology Application Project of Lishui (2011JYZB02).
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