Horse Side Vet Guide ®

Equine Health Resource

Single or Multiple Lumps, Bumps, or Growths on Back

Code Orange - Call Your Vet at Their First Available Office Hours

Code Yellow - Contact Your Vet at Your Convenience for an Appointment

Code Orange - Call Your Vet at Their First Available Office Hours

  • If the mass is large, painful or seems to be growing rapidly.

Code Yellow - Contact Your Vet at Your Convenience for an Appointment

  • If the mass is small, non-painful or seems to be only growing slowly.

Clearly defined lumps and bumps (not more generalized swellings) on a horse’s back are common, and can result from a variety of causes including saddle induced traumatic injury or other disease processes. The inflammatory condition Nodular Necrobiosis is one of the most common diagnoses for a small firm bump here. A hard skin growth in a gray horse is melanoma until proven otherwise. Hematomas can develop in this area too. Rarely, sarcoids and other skin tumors may also develop on the back. A more rare cause of bumps right down the center of the back is called Dermoid Cysts.

One unique feature of growths on the center of the back is that they can be irritated by the saddle and result in loss of use. Any mass that is likely to be irritated by tack is problematic, and so it makes sense to eliminate it as soon as possible. A definitive diagnosis and aggressive treatment is usually the best course of action.

If there is only a single or a few masses, then surgical removal and submission of the tissue to a laboratory for diagnosis might be the most practical approach. If there are many bumps, a more body-wide approach to treatment might be needed.


Carefully evaluate your horse’s back noting the characteristics of the growths such as the size and number of bumps. Are they symmetrical on left and right? Are they right on the center of the top-line? Press on the bumps to assess their consistency, whether there is a pain response, and for heat or underlying swelling. Look and feel for bumps elsewhere on the body. Take a photo of the bump(s) and send it to your vet for discussion. Use a ruler for size reference.


Some lumps and bumps are very common in this area and a diagnosis may be presumed by your vet. An example is Nodular Necrobiosis. Treatment depends on diagnosis, but sometimes response to treatment is a very useful diagnostic in itself.

If there are just a few bumps, your vet may choose to remove them surgically. The only way to know specifically what the disease process is is to submit the tissue to the laboratory for definitive diagnosis. If nodular necrobiosis is the presumed diagnosis, your vet may try injecting under the masses with a steroid to see if they resolve.

Author: Doug Thal DVM Dipl. ABVP


Hillyer LL1, Jackson AP, Quinn GC, Day MJ Epidermal (infundibular) and dermoid cysts in the dorsal midline of a three-year-old thoroughbred-cross gelding. Vet Dermatol. 2003 Aug;14(4):205-9.


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