Mr T the horse

Case study: Mr T’s melanoma


Meet Mr T, who earlier this year developed a slight swelling on the left hand side of his back, under the saddle region. He didn’t seem overly bothered about this swelling, but his owner asked Sarah to check it out as they were concerned that it was steadily growing bigger.

Sarah was a bit perplexed – the swelling felt to be a solid lump under the skin attached to one of Mr T’s ribs. The lump was therefore ultrasound scanned, which showed it was a soft tissue mass and was spreading between the ribs and expanding down towards his chest cavity. Given its location and the fact that it was growing bigger and likely to be causing Mr T some discomfort, it was decided that it was best off being removed. A biopsy was taken to determine what the mass was and the degree of malignancy as this would determine the ‘margin’ required at surgery.

Mr T in melanoma surgery


For his surgery, the team were assembled with Guy operating and Charlotte performing Mr T’s anaesthetic. Due to how close the mass was to his lungs, Mr T was fully anaesthetised, as any sudden movements on his part could have resulted in his thoracic cavity being inadvertently entered. With Mr T nicely asleep, Guy carefully dissected the mass away from the normal tissues surrounding it. A drain was placed to help reduce fluid build up where the mass had been removed, and once he was up and awake, Mr T had a belly bandage placed to help keep his surgery site clean. Thankfully, the mass was a melanoma, which is a relatively common tumour in older grey horses, albeit in Mr T it was in a very unusual spot!


Melanomas are typically found in the perianal region, under the tail, inside the sheath, around the vagina or inside the mouth, although some horses will develop them under the skin elsewhere or internally.

Melanomas themselves are not generally too much of an issue if located externally, unless they become very large and ulcerated and therefore sore, but removal is most straightforward whilst they are small. Also, there is some evidence that the fewer melanomas a horse has present, the less they will go on to develop, so early removal is now generally recommended.