Blisters or bubbles on tangs fin? Diagnosis?

[docmal]

I purchased an achilles tang this weekend. He had what apeared to be very small fin damage on his dorsal fin.

After a day this damage apeared to be inflated like a blister or bubble.

After two days the initial blister/bubble seems to have split into several blisters or bubbles.

These bubbles are about the size of the tang's eye and reside on the dorsal fin half way between the middle and rear points.

The tang has gotten along well with other tank mates. He is eating plenty mysis, brine and calurpa. The bubbles don't apear to be negatively affecting him yet.

Can anyone diagnose this?

 

[Pandora]

Any possibility of getting a photo? Sometimes, a cyst can form on the rays of fins, though it's not common--sometimes comes about when a fish gets a minor infection in that area, and it's the body's reaction to this: walling it off. There are some pics on my disease site of cysts (click on the red home icon at the top of my post, and then Disease). The other thought is lymphocystis, also shown elsewhere there, but I wouldn't describe it as "bubble like"... more like small tumor like growths.