I just got back from the vet's office with my dog Saber after his recent surgery. He either had Hemangiopericytoma or a fatty tumor. Theresults will be back in 7-10 days to determine which one. In this case a tumor would be better because the Hemangiopericytoma will eventually grow back. He's all fine and well. At the moment he's laying on the foldout couch bed from the after effects of theanesthesia. I got to see the whatever it was that came out of him. It was cut in has since the other half went for a biopsy. Look at the size of your palm (ages 13-15), that's about the size it was, the half of it at least.

Now, because your probably asking a Hemangiopericytoma is the following.

Hemangiopericytoma: consists of numerous vascular channels with plump endothelial nuclei and a surrounding, tightly packed proliferation of oval and spindled cells with dark nuclei and a moderate amount of cytoplasm.
Endothelial: thin layer of specialized epithelium lining the interior surface ofblood vesselsforming an interface between circulating blood in the lumen and the rest of the vessel wall.
Epithelium:a tissue composed of a layer of cells.