It is a lymph node that probably gets bigger and smaller when you are about to get sick. Larger, that is, when you are going to get sick.
Do you have any symptoms? Any pain in the ears or behind the ears, dizzyness or vertigo or any other symptoms. It could be a benign tumor called an acoustic neuroma but you would need an MRI to check.I suppose it could be a cyst as well. Cysts are more common.
Never experienced any of those symptoms - they're just ... there :/
Since you don't have any symptoms it may be cysts. I would get them checked out though.
mkh9
As I stated in the very first post, they are just lymph nodes. Don't worry about them. I have it behind my right ear. DO go to the dr asap if they change in size (get bigger). :-)