Red lump under hamsters tail

[Kataust1405]

I've got a male Syrian he's about 4 months old now and he's got red lump looks swollen under his tail, I swear it wasn't there a week ago and I've just noticed it. Googled and some say it's a tumor, some say it's his testicles, some say it's something called wet tail??
He's absolutely fine in himself totally normal behaviour and eating normally, I am such an over thinker. If it's his testicle why haven't I noticed them before. They look red and a bit swollen. Any advice or anyone experience the same. I can try and get a photo if it helps.

 

[Maz]

Hi. A photo would help But if he's four months old and it's just appeared, it's likely to be one of his testicles poking out Is it there all the time or does it disappear sometimes? Their testicles tend to descend and "pop out" when they're warm or relaxed and he's probably just reached puberty.

It won't be wet tail - he'd have excessive diarrhoea if it was that and be very unwell.