I have a grey Andalusian Stallion. He has a large amount of melanomas around his anus.They do not seem to bother him except when he is deficating. Although he is fed on soaked food to keep his manure soft. He seems to be rolling a lot lately and biting his sides now and again. I have ruled out colic as he eats and drinks no problem and gets excited when he see's the other horses. He seems happy within himself but I am worried in case he has internal melanomas.
He is 17 years old.
He has also started to lose hair around his eyes and muzzle.

Melanomas in Andalusians are very common, and almost all of them have it.

It is very possible for him to have these tumors on the inside, and although he is still acting normal, he is probably having small colic spasams. Excessive rolling, biting at the sides and so on are classic signs of colic.. but apparently these symptoms aren't bad enough for him to go off feed and become depressed.

Unfortunately, Melanoma's are going to be the end of this horse. Especially since the tumors are around his anus. I have seen an Andalusion stud with melanomas so large around his anus, it actually covered the opening to his anus. He ended up dying of colic due to these melanomas.

My advise, keep him comfortable and keep your vet on speed dial. Talk to your vet about possible surgeries for his anus to make him more comfortable.

Good luck to you and your boy.