Not the most helpful thing I'll ever post but.... Hector won't let me stroke him & Cleo will only let you stroke below the shoulders so I can't say what's going in there. However, if they are anything like the cats then I guess it's a mixture of cartilage & the muscles used to help them move their ears. I'd say as it's something he has identically on both sides it is unlikely to be a growth or anything untoward. But always best to check rather than worry - I would've.
(I shall file this under "blind leading the blind"
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