Tumors of extravascular (perivascular cell) origin do not include hemangiopericytoma! So Hemangiopericytoma (HPC) does exist, but where? It is now classified as an intermediate type of fibroblastic/myofibroblastic tumor and is discussed together with solitary fibrous tumour (SFT) as a group of tumors, but there is still some controversy so the ICD codes for the two diseases are currently separate. Hemangiopericytoma is 70% benign and 30% malignant and there are no criteria to predict the biological behavior. Personal opinion : Unlike hemangiopericytoma hemangiopericytoma is a malignant tumor originating from bone vascular epithelial cells and is divided into aggressive hemangiopericytoma and hypodifferentiated malignant hemangiopericytoma according to pathological changes. According to WHO, it accounts for only 0.16% of primary bone tumors and is even less common than endothelial cell tumors. The tumor is mostly found in young people aged 21-30 years old, and it is usually found in the pelvis and femur. The endothelial cells were normal in shape. The epithelial cells were interdigitated, proliferated, irregularly arranged around the vessels and compressed the vessels. The epithelial cells were round, oval or spindle-shaped with large deep-stained nuclei, detailed chromatin, abundant cytoplasm and eosinophilic, whereas malignant cells had variable-sized nuclei, marked heterogeneity, frequent splitting images and silvery-stained cytoplasm. Reticulate fibers could be seen scattered among the cells.