growth on arm

my male chihuahua is 14 yrs. and has developed a blood filled growth on his arm.  we have taken him to 3 different vets and no one knows what this is. we were just told to drain it whenever it fills with blood. please help.

[Jaybay]

Hello and welcome!  I wish I had some advice for you, but this one is beyond my knowledge and ability.  Your question would be best answered by Dr. Cheng on Med Help's Ask a Vet forum.  Participation is free, but there is a 4 question per day limit, so keep on trying until you get through.  To access the forum, scroll far down on the right side of this page and click on the "Ask a Vet (Pet Health)" link.  

You've done a great job of taking care of your chi since he's 14 years old!  I hope this growth turns out to be nothing too serious.  Keep on trying!  :-)