Solitary Fibrous Tumor : Histology
Classical solitary fibrous tumor is hypocellular as compared to the hemangiopericytoma pattern. It is composed of bland spindle cells arranged haphazardly (patternless pattern) in an abundant hyalinized stroma. The degree of cellularity is often variable ranging from large hyalinized zones with few or no cells to areas with moderate cellularity. The staghorn vessels are less numerous than in hemangiopericytoma pattern.