It does look like mistletoe! Should I remove it?

yes a picture is definitely needed here please. sounds like it could be a hemi-parasite plant
how old/large is your oak?
do you get mistletoe in the US?

another thought is pin oak a chiera plant? if it is then damage can make a branch grow from the other genetic stock.

if which i think it is its mistletoe its only a semmi parrasite and wont actualuly hurt your oak tree .

Thanks for the feedback. It is quite amazing to see that green stem just growing out of the bark. I have heard the Christmas stories but never knew how they grew. I guess when word gets around all the kids will park under my tree in hopes of a kiss!

You lucky person, I have tried many times to get mistletoe to grow on my trees.
I feel pleased that I thought of it. the photo confirms it is mistletoe.

It taps into the sap of the tree for its water and mineral supply and then photosynthesises with its leaves. Brilliant plant.

im trying to grow it on my acer as we speak fingers crossed . you should charge a $1.00 a kiss lol .

I have since noticed that many of the Pin Oaks in my neighborhood have very large clusters, some trees have many. I don't want it to take over/harm my tree and I am tempted to remove the branch it is on yet I hear both of you are trying to grow it.
Am I overreacting?

yes your overreacting as it is only a partial parrasite so doesnt take much from the host . if you want to find out more google mistletoe and you will feal better about it or at least put your mind at rest .