[71] Primary Myoepithelioma of the Orbit

Kinjal Shah, Yaxia Zhang, G Petur Nielsen, Andrew E Rosenberg. University of Miami, Miller School of Medicine-Jackson Memorial Hospital, Miami, FL; Massachusetts General Hospital, Boston, MA

Background: Myoepithelioma is an uncommon tumor that has been described in a variety of different anatomic sites including the soft tissues. Histologically, its morphologic heterogeneity can cause confusion with a variety of different neoplasms. Myoepithelial tumors arising in the orbit are rare and to increase our understanding of these neoplasms we reviewed our experience with 3 cases.
Design: The study cohort was identified from one of the author's consultation files and from the surgical pathology files of Massachusetts General Hospital. The clinicopathologic characteristics of the tumors including their histologic and immunohistochemical features, and status of translocation involving the EWSR1 gene were analyzed. Ultrastructural study was also performed in 1 case.
Results: The patients included 3 females ages 5, 13 and 16. The tumors arose in the orbital soft tissues. Histologically, the tumors were solid, had a lobulated growth pattern and were composed of spindle to epithelioid cells with eosinophilic cytoplasm. The tumor stroma varied from myxoid to hyalinized. In one case scattered duct-like structures lined by cuboidal cells were present. The tumor cells lacked cytologic atypia, mitotic activity and necrosis. Immunohistochemically, the tumor cells expressed s-100, EMA, keratin, p63, desmin, SMA and calponin. The tumor cell were negative for GFAP, myogenin, MYOD-1 and CD34. Electron microscopy performed on Case 3 showed tumor cells with reduplicated basal lamina, short cellular processes and cytoplasmic filaments with focal densities, features consistent with myoepithelial differentiation. Fluorescent in situ hybridization performed on Cases 2 and 3 for translocation involving the EWSR1 gene on chromosome 22 was positive for a rearrangement. The tumors were treated with conservative resection and follow-up ranged from 3 to 46 months. Case 3 had a local recurrence 18 months after initial resection and underwent subsequent resection, and currently has no evidence of disease based on a recent MRI.
Conclusions: Myoepithelial tumors of the orbit are rare and can be confused with a variety of different neoplasms including rhabdomyosarcoma. Immunohistochemically, they often express S100, EMA, keratin and can have rearrangement of the EWSR1 gene. Biologically, these tumors can locally recur and the goal of treatment, if possible, is surgical resection with negative margins.
Category: Bone & Soft Tissue

Tuesday, March 5, 2013 1:00 PM

Poster Session IV # 13, Tuesday Afternoon

 

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