Indian Journal of Pathology and Microbiology

CASE REPORT
Year
: 2020  |  Volume : 63  |  Issue : 2  |  Page : 267--269

Myxoid meningioma: A case report of an extremely rare subtype of metaplastic meningioma


Seema Rahar1, Arvind Ahuja1, Purnima Bharati1, Minakshi Bhardwaj1, Ajay Chaudhary2,  
1 Department of Pathology, PGIMER and Dr. RML Hospital, New Delhi, India
2 Department of Neurosurgery, PGIMER and Dr. RML Hospital, New Delhi, India

Correspondence Address:
Arvind Ahuja
Department of Pathology, Room No. 323, PGIMER and Dr. RML Hospital, New Delhi - 110 001
India

Abstract

Myxoid meningioma is a rare histological variant of meningiomas grouped into the subtype of metaplastic meningiomas (World Health Organization grade I) characterized by the presence of myxoid areas and meningothelial cells along with unique ultrastructural features that help distinguish it from other meningiomas. Hereby, we report a case of a myxoid meningioma in a 40-year-old female who presented with altered sensorium and loss of consciousness. Imaging studies showed a dura-based solitary mass located in the left frontal lobe. The tumor was excised completely. Histopathology revealed a benign appearing myxoid neoplasm with uniform elongated cells, without any atypia and a very low mitotic activity. Immunohistochemical stains showed positivity for vimentin and epithelial membrane antigen confirming the diagnosis of myxoid meningioma. Only seven cases of myxoid meningioma have been reported till date in the literature and ours is the eighth case.



How to cite this article:
Rahar S, Ahuja A, Bharati P, Bhardwaj M, Chaudhary A. Myxoid meningioma: A case report of an extremely rare subtype of metaplastic meningioma.Indian J Pathol Microbiol 2020;63:267-269


How to cite this URL:
Rahar S, Ahuja A, Bharati P, Bhardwaj M, Chaudhary A. Myxoid meningioma: A case report of an extremely rare subtype of metaplastic meningioma. Indian J Pathol Microbiol [serial online] 2020 [cited 2020 Jul 15 ];63:267-269
Available from: http://www.ijpmonline.org/text.asp?2020/63/2/267/282679


Full Text



 Introduction



Myxoid meningioma is a rare subtype of metaplastic meningioma [World Health Organization (WHO) grade I] with unique histological and ultrastructural features.[1],[2] We hereby present a case of a myxoid meningioma, a rare histological variant of meningiomas grouped into the subtype of metaplastic meningiomas in a 40-year-old female to highlight the important histological features that are imperative for making an accurate diagnosis of this rare entity. In the English literature, to best of our knowledge, only seven cases of myxoid meningioma have been reported till date and this is the eighth case.

 Case Report



A 40-year-old female presented to our hospital with altered sensorium and sudden loss of consciousness. She had a history of on and off headache for 2 years with sudden worsening of headache and vomiting since the last 3 days. On examination, her bilateral pupils were dilated and nonreacting with Glasgow Coma Scale score of E1, V-1, and M2. Planters were bilateral extensors. Magnetic resonance imaging of brain was suggestive of extra axial, dura-based lesion in the left frontal lobe measuring 8 × 5 × 5 cm with mass effect, midline shift of 14 mm to the right, perilesional edema, and brainstem infarct [Figure 1]a. The patient underwent left frontotemporoparietal decompressive craniotomy. On durostomy, a large mass lesion was seen arising from the dura in the left frontoparietal region. The dura was adherent to the underlying brain. The tumor was highly vascular, greyish, firm, attached to left lateral one-third of sphenoid wing with a well-defined plane separating it from the surrounding brain. It was completely excised along with the overlying dura. Grossly, an encapsulated mass measuring 8.5 × 5 × 5 cm with attached dural membrane measuring 9 × 3 × 0.2 cm was noticed. External surface was irregular with grey to dark brown areas. Cut section was soft to firm with grey-white and grey-brown solid areas. Areas of hemorrhage along with mucinous areas were also noted [Figure 1]b.{Figure 1}

On microscopy, multiple sections examined showed a tumor comprising predominantly of large myxoid areas, uniform cells, and with focal areas revealing increased cellularity comprising meningothelial cells arranged in whorls with oval nuclei and delicate chromatin. Large areas of hemorrhage were also noted. Mitotic activity and necrosis were not evident [Figure 2]a and [Figure 2]b. The myxoid background stained strongly with Alcian blue (pH 2.5) [Figure 2]c and [Figure 2]d. Immunohistochemical staining revealed immunoreactivity for epithelial membrane antigen (EMA) and vimentin [Figure 3]a and [Figure 3]b. However, GFAP was negative and Ki67 LI was approximately 5%–7% [Figure 3]c. Based on morphology and immunohistochemistry (IHC) results, a diagnosis of myxoid metaplastic meningioma, WHO grade I was rendered.{Figure 2}{Figure 3}

 Discussion



The WHO classification of the central nervous system (CNS) tumors defines various types of meningiomas. Most of the WHO grade I meningiomas are slow-growing, including some rare subtypes such as metaplastic meningioma, microcystic meningioma, and secretory meningioma.[2]

Metaplastic meningioma is a rare subtype of WHO grade I tumor. These meningeal tumors are referred to as “metaplastic” because their transformed neoplastic cells demonstrate the full histological characteristics of the cells they mimic.[1] It includes a wide range of subtypes depending on the mesenchymal differentiation. In addition to the myxoid type, osseous, cartilaginous, lipomatous, and xanthomatous subtypes are categorized in this group.[1],[2] The myxoid appearance in the myxoid subtype is attributable to the excessive presence of hyaluronic acid and chondroitin sulfate, which imparts strong aqua blue staining when stained with alcian blue at an acidic pH of 2.5.[1],[3]

[Table 1][3],[6],[7],[8],[9],[1] depicts all the cases of myxoid meningioma reported till date. The presenting age of patients is broad ranging from 7 to 70 years and commonly involves the left hemisphere. Most of the patients are females. Headache and altered sensorium were the most common symptoms.{Table 1}

A careful histological interpretation and panel of immunohistochemical stains are essential to make an accurate diagnosis and to differentiate from other myxoid CNS tumors. Chordoid meningioma, a WHO grade II meningioma, also has a myxoid stroma but differs in cellular appearance from the myxoid meningioma.[4],[5] Unlike the myxoid metaplastic meningioma cells, chordoid cells are polygonal in shape with round nucleoli and abundant vacuolated cytoplasm and the cells are arranged in a cord-like fashion. Moreover, in myxoid meningioma, lymphocytic infiltrate is never seen.[1] It is also important to rule out myxoid solitary fibrous tumor which is EMA-negative;[10] myxopapillary ependymoma which has papillary features and rosettes along with GFAP positivity;[11] metastatic or primary low-grade fibromyxoid sarcoma[12] which can also be ruled out by IHC as they are positive for vimentin and negative for EMA and S100 unlike myxoid meningioma. IHC confirmed our case to be of meningioma. Interestingly, a higher Ki67 LI (5%–7%) was obtained in our case in contrast to all other reported cases in which it was low.

Dot-like EMA positivity is seen in cases of ependymoma and this was a unique immunohistochemical feature seen in our case, however; closest differential was myxopapillary ependymoma which was clearly ruled out as no papillary structures were seen in our case and IHC for GFAP was negative.

There are no known studies with long-term follow-up that have evaluated the natural course of this tumor and its anticipated prognosis, however; as this lesion has low histological grade, it is believed to carry a good prognosis with little chance for recurrence.[1]

 Conclusion



Myxoid meningioma is a very rare subtype of metaplastic meningioma, and hence this case is being reported to further enrich our knowledge about this rare entity. Our case showed two unique immunohistochemical features. First, higher Ki67 LI of approx. 5%–7% and second dot-like EMA positivity which has not been reported earlier.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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