Tumour Or Lymphocystis

I have mentioned in other threads that my new plakat betta, which I bought in August, has a lump. It first appeared a couple of weeks after I got him as a raised scale, as if he'd caught himself on the decor. But it got bigger and bigger.
I'm not sure what it is, but I've narrowed it down to a tumour or lymphocystis. It doesn't look like a lot of pics of lymphocystis, but rather than risk it he's been moved to a tank on his own, and I use a separate siphon tube and bucket for his water changes.

I've attached a few photos. Some of them are a bit blurry as he did not want to co-operate    but the lump is clear enough.

Anyone any ideas which it is?

The lack of white was the thing that made me wonder. The lump does get a speck of white but it comes and goes. The bigger it gets, the less it looks cauliflowery. If it is a tumour, at least the fish he was with in the 50 litre tank should be safe from infection. But I'll still keep him on his own, just in case.

He was sold as a bright blue dragon half moon plakat. He was pale blue when he arrived, I suspected that was due to the trauma of being posted, and as you can see he is now bright blue. And he's definitely a half moon; the edges of his tail are maybe slightly over 180^o apart.
I swore I'd never get another dragonscale after what happened to the eyes of my last one, but I thought this one didn't look as if he had very thick scaling. But, look at his left eye in the first photo.......



Old forum members might remember the dragonscale betta that died just recently. I posted the first photo below on the old site when I first got him. A year or so after that was taken, he developed finrot after his tail was bitten by a frog. I finally stopped the rot with esha 2000, but his tail never looked the same again. But the reason for posting these pics is to show what can happen to the eyes of a dragonscale betta. These fish have thicker than normal scales, and the scaling can grow over their eyes. These pics were taken shortly before he died.

The time has come.

My poor plakat was suffering. He had been hiding away with his fins clamped up and the lump had got much worse. Over the weekend it burst open and it was a horrible spongey white. And he was also growing more lumps down his side. So this morning I put him to sleep. I just couldn't bear the thoughts of him being covered in several lumps like the first one.