Yeah, that's not right. I don't know what it is, but having butchered about 50 or 60 birds this year, chickens, ducks, turkeys, and quail, I can honestly say I've not seen anything like that. The ducks I butchered were, coincidentally, 2 years old also, some of my excess Rouens, and they had nothing like that inside.
I can only speculate -- some kind of tumors, may fibroids similar to uterine fibroid tumors in women? Of just some kind of abdominal fat deposits -- we know ducks are a very fatty meat, and domestic ducks given a good diet do eat a lot and get fatty.
Honestly, I've never heard of injecting ducks with hormones, no any poultry, and I'm sure it wouldn't be legal in the US. But who knows -- that is weird , maybe you could e-mail the photo to your state's Dept. of Agriculture's veterinary pathology service and ask them what it could be?