The tumor is composed of a somewhat monomorphic population of high-grade malignant cells arranged in diffuse sheets. Some cases show alveolar or trabecular growth pattern. The tumor cells are round to oval with a large vesicular nucleus and prominent nucleolus. A characteristic feature is the presence of a large cytoplasmic eosinophilic globule that is composed of intermediate filaments. This globule may displace the nucleus creating a plasmacytoid or rhabdomyosarcomatoid appearance.