9 December 2015 - Case of the Week #373

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Case of the Week #373

Clinical history:
A 61 year old man presented with a left brain mass, which was resected by craniotomy. The surgeon believed the mass arose from the dura.


Micro images:

Smears:


Additional smears:


Frozen section:


H&E images:


Additional H&E images:



What is your diagnosis?































Diagnosis:
Angiomatous meningioma, WHO grade I
Necrosis associated with angioembolic material (elsewhere)


Discussion:

Immunostains were obtained:

BCL2

CD34


EMA


MUC1

Ki-67


p63

PASD


S100



Meningiomas are neoplasms which originate from meningothelial cells. Most arise within the cranial cavity and are dura based. They may occur in childhood or adolescence, but are more commonly encountered in middle or later adult life. Females are more commonly affected, and there has been evidence that their growth is subject to hormonal influence (Rosai and Ackerman's Surgical Pathology, 2011). Angiomatous meningioma, constituting roughly 2% of meningiomas, is a rare histological variant of meningioma whose vascular component exceeds 50% of the total tumor area (Int J Clin Exp Pathol 2013;6:695, Am J Surg Pathol 2004;28:390). Compared to conventional meningioma, it has a high male to female ratio and more frequent peritumoral edema (Int J Clin Exp Pathol 2013;6:695).

On gross examination, meningiomas are solid and lobulated, and broadly anchored to the dura mater.

On histology, angiomatous meningioma features abundant blood vessels with at least focal classic meningothelial differentiation (syncytial cells with indistinct cell membranes and eosinophilic cytoplasm, intranuclear pseudoinclusions and a lobulated architecture with meningothelial "whorls"). Immunostains are strongly positive for EMA / MUC1 and S100. BCL2 is negative in tumor cells and only a focal area of tumor cells stain positive for p63. Both E-cadherin and N-CAM show light focal staining. CD34 and PASD highlight the dense vascularity present in the tumor. Ki-67 proliferation is ~1%.

The WHO / Mayo Clinic criteria stratifies meningothelial tumors into meningioma (WHO grade I), atypical meningioma (WHO grade II) and anaplastic meningioma (WHO grade III), based on features such as mitotic activity, cellular density, growth pattern, atypical cellular features (macronucleoli, high N:C ratio) and presence of necrosis (Rosai and Ackerman's Surgical Pathology, 2011). The present case showed no atypical features, and is thus classified as WHO grade I.

The differential diagnosis might include hemangioblastoma and hemangiopericytoma, especially if interpreting a small fragment of tissue from, for example, an intraoperative consultation (Indian J Pathol Microbiol 2008;51:53). Immunohistochemistry can be helpful in equivocal cases, with EMA, CK and progesterone positivity confirming a diagnosis of meningioma. Hemangioblastoma would express inhibin and NSE.

The prognosis is favorable, similar to other types of WHO I meningiomas, and gross total resection is the treatment of choice. Patients with residual tumor after surgery can benefit from radiation therapy (Int J Clin Exp Pathol 2013;6:695, Am J Surg Pathol 2004;28:390).


Discussion by Dr. Jennifer R. Kaley, University of Arkansas for Medical Sciences (USA).