Help...what is this mass/creature on my Mimic Tang's fin??

[October]

Can anyone please diagnose this mass on the dorsal fin of my mimic tang? It appeared overnight and has slowly grown in size over the past 2 weeks. Almost looks like I can just pick it off but I can't catch the fish. Could this be some sort of parasite and will it fall off on its own?

 

[October]

Here's another pic from a different angle...

 

[ngoodermuth]

It's hard to tell from the photos, it could be some sort of trematode worm or an isopod. A freshwater dip might dislodge it. Or like you mentioned, manual removal.

 

[Jahalu]

Perhaps it's lympho?
Here's a link:
https://www.reef2reef.com/threads/lymphocystis.257461/