What causes lumps on a deer’s skin?

What causes lumps on a deer’s skin? Are these lumps dangerous for the deer?

Although these lumps look nasty, they’re actually nothing serious. The hump is either a papilloma or a fibroma, benign tumours found mostly on the skin of deer, though they may also occur on other wildlife. In deer, the cause is a virus. The tumours aren’t all that uncommon but they don’t seem to bother the deer unless they get very large. In that case, they can interfere with walking or other movement.