Anyone know what this is growing on this acan?

[crny1]

I have noticed this getting bigger and bigger over the last 2 weeks. I took turned the lights on just for this picture cause when the acan is fully inflated not as much shows. It’s the same color as the main color of the flesh on the acan. Seems inflated. Just never seen it before. Ideas?

 

[BranchingHammer]

Sponge?

 

[crny1]

Definitely not a sponge. Seems inflated and has movement with the flow