Myoepithelial carcinoma of the orbit: a clinicopathological and histopathological study

Two cases of invasive myoepithelial carcinoma arising from the paranasal sinuses and invading the orbit are presented. Patient 1, a 53-year-old man, had a 3-month history of proptosis, pain and epiphora of the right eye. The second patient, a 24-year-old man, had for a week been complaining of protrusion of his left eye and of orbital pain. Computed tomography scan and magnetic resonance imaging revealed tumour masses in the frontal, ethmoidal and maxillary sinuses with invasion of the orbit and the frontal lobe. Biopsies from both cases showed spindle and epithelioid tumour cells. Mitotic figures were frequent. Immunohistochemical staining showed positive reaction for bcl-2, calponin, cytokeratins, CD99, S100, muscle-specific antigen, smooth muscle antigen and vimentin. The Ki-67 index was between 30-50% and 5-25%, respectively. Ultrastructurally, intermediate filaments, perinuclear tonofilaments and desmosomes were present. Based on these findings, a diagnosis of myoepithelial carcinoma of mixed cell type in both cases was evident. Both patients died shortly after the diagnosis was made even though both underwent radical surgery. Myoepithelial carcinoma of the paranasal sinuses is very rare and only six cases have been reported previously. We present the first two cases of myoepithelial carcinoma in the paranasal sinuses with invasion of the orbit. This is also the first report of myoepithelial carcinoma arising in the ethmoidal sinus.