December 13, 2021 Case of the Week

60s female 
Canthus mass
What's your differential?

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Diagnosis: Meningioma (CNS WHO grade 1), periorbital tissue Fibroadipose tissue and skeletal muscle infiltrated by nests of epithelioid cells with round to elongated nuclei and delicate chromatin, forming vague whorls.

The tumor cells are positive for EMA and progesterone receptor; AE1/AE3 is negative supportive of the above diagnosis. Low Ki-67 expression is consistent with low-grade.