Actin
Cytokeratin
This well circumscribed tumor is composed primarily of interweaving fascicles of spindle cells having a moderate amount of eosinophilic cytoplasm, blunt-ended cigar-shaped nuclei with stippled, occasional vesicular chromatin and inconspicuous nucleoli. Occasional large pleomorphic cells are seen. Mitotic figures are easily found, and average eight per ten high powered fields. Focal necrosis and myxoid changes are present. Desmoplasia is not seen. Immunohistochemical stains for smooth muscle actin and desmin are diffusely, strongly positive. Immunostaining for vimentin, myoglobin, cytokeratin, and the S100 protein are negative.
