I've seen a few of those over the years. Don't know the cause but it eats the same so doesn't bother me.

"Lygocoris communis" (Knight), green apple bug injury? They in your state? Looks like:
http://extension.psu.edu/plants/tree-fruit/insects-mites/tarnished-plant-bugs-other-plant-bugs-and-stink-bugs

http://extension.psu.edu/plants/gardening/fphg/stone/insect-and-mite-pests/plant-stink-bugs
and more info:
http://cropipm.creativedonkeys.com/english/apples/insects/tarnished-plant-bug.html

See fig 4-68 (image) in hyperlink below and this one:
http://www.agrireseau.qc.ca/references/21/banqueimages/html/WebInsecte/Pommier/Album220.html which leads me to believe this is the culprit.

Here is a link that might be useful: Tarnished plant bug and other stinging insects

This post was edited by Fascist_Nation on Sat, Feb 1, 14 at 16:10

FCCO

It looks like plum curculio damage to me. If so, the scar
would be a small crescent shape in July but as the apple
enlarges it becomes the giant lump you see on your apples
when ripe.

I attached a shot of curulio damage on ripe apple.

FCC:

Here is a shot of curculio scars on young apple.

Thanks for the feedback! I contacted the cooperative extension here in PA and they agreed with you that the damage was Plum Curcurlio. Your picture looks a lot like mine, but most of the pictures of PC damage on the web show patches that are flat and not raised, and this made ID difficult. My wife and I did some scouting around when we first saw the damage when the apples were tiny, and I remember now that she did find a snout-beetle hanging around and that I had thought that PC might be the problem. I was using Malathion and Triazicide (Cyhalothrin) as insecticides, but I see from my notes that timing may have been poor. I sprayed some fungicide late in the bloom period on May 10 and the next entry for spraying was June 4. At that point, I noted that most of the gumball-sized apples already had small bite marks (tiny and round, not really crescent-shaped). I might have had another spray in there that I did not record, but maybe not. My current thoughts for this year are: 1. Take better notes so I can learn from my efforts. 2. Spray the apples right before bloom starts and definitely right after bloom ends to get those darn curculios!