Contributed by Sarika Jain, MD and Raja Seethala, MD.
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A 52 year old female came with intermittent left facial paresthesia/ hyperesthesia and swelling since 3 weeks.
CT scan shows a 5 cm left masticator space mass with skull base erosion and orbital erosion.
Sections show random proliferation of spindle cells and epithelioid cells arranged in patternless pattern with thick bands of collagen. The tumor also showed areas with patulous staghorn shaped branching vessels (hemangiopericytomatous pattern). There were some hypocellular areas, myxoid change and areas of necrosis. The mitotic count was 18/10 HPF.
Figure 1 shows tumor with infiltrative border.
Figure 2 shows the classic hypocellular and hypercellular areas.
Figure 3 shows the HPC-like areas
Figure 4 shows the epithelioid morphology.
Figure 5 shows multiple mitotic figures.
Figure 6 shows vascular invasion.
Immunostains show positive staining for CD34, BCL2 and CD 99 and negative staining for S-100, actin, AE1/3 and desmin (Figures 7, 8, 9).