I haven't seen these before...must have been 20 of them. Some larger than other. Cut them open and there wasn't really anything there...seemed like blood. Keep in mind these were on top of the muscle surrounding the food and windpipes, not coming out of them. I have only just started to butcher the neck to make neck roasts, so I am not sure if this is common or not.

Deer (also pictured) seemed very healthy to me.