If you own a grey horse over the age of 15 years, it is likely your horse has some tumors on the skin called melanomas.  In fact, 80% of grey horses over the age of 15 have some melanomas and 60% of these tumors involve the skin.  The most common place for these tumors is the area around the anus, vulva and tail. Some of these tumors may even ulcerate and bleed but most are simply benign masses of various sizes.  In general, these masses do not cause a problem unless they get so large they cause a physical problem.  Since they occur around the anus, some of these tumors can make it difficult for the horse to have a bowel movement.  However, some melanomas can occur in other areas such as the mouth, eyes, salivary glands, penis, and the nasal cavity.  They can even sometimes occur around the heart and abdominal organs. 

Treatment of the small masses in grey horses is probably not necessary or recommended.  It was once thought that removal of the masses could cause them to spread and although it is now believed this is not the case, removal of some of the tumors can cause others to grow larger.  However, surgery has been effective in many cases of tumors that are causing problems.  Smaller tumors are also being treated successfully with cisplatin beads.  Cisplatin beads are small little marble-sized beads that contain an anticancer drug called cisplatin that is inserted surgically in the tumor.  Another treatment for melanomas is the oral use of the drug cimetidine, which has been shown in some cases to shrink the tumors.  However, the drug must be given twice daily so it takes a lot of dedication and in many cases is not effective.