What are spindle cells? I recently had a biopsy done on a sub mucossal mass in my stomach . When the growth was noticed it was very small and thought to be a pancratic rest, after endscopy it was thught to be a gist tumor. However the results showed spindle cells. They slides being sent out for further tests. I m not sure why? Or even what spindle cells are. I thought a gist tumor wasn t considered a bad thing Thank you