What you see. The starting point for addressing any equine health related issue is your observation.


Lump, Bump, Growth on Sheath or Penis


A horse's penis and sheath may develop a variety of lumps, bumps or growths. This is especially common in older horses. A bumpy mass within the sheath may merely be an accumulation of smegma, the pasty material naturally produced by the sheath. Smegma usually is dark gray to black, but in pink-skinned horses it can be orange to pink.

Accumulation of smegma at the end of the penis, a "bean", is removed during a routine sheath cleaning.

Lumps and bumps felt within the mass of the sheath can also be tumors. The most common of these are melanomas (in gray horses) or squamous cell carcinoma in lightly pigmented horses.

  • Code Orange

    Call Your Vet at Their First Available Office Hours
    • If the swelling is large, painful or growing rapidly.
  • Code Yellow

    Contact Your Vet at Your Convenience for an Appointment
    • If you consider this a chronic and relatively mild problem that is not changing rapidly.

your role


What To Do

Assess your horse's general health using the Whole Horse Exam (WHE). Also assess the penis and sheath as well as you can, and share your findings and concerns with your vet. If you normally clean your horse's sheath, then do so. A photo of a growth may be helpful to your vet to determine the urgency of an exam.

your vet's role

Routine veterinary inspection of this area is important because tumors and other disease of the sheath are relatively common, especially in older horses. Vets often tranquilize horses before cleaning their sheath to relax the penis and make the process easier. Tranquilization allows much better visualization of the penis and sheath.
Questions Your Vet Might Ask:
  • How old is the horse?
  • What breed and color is the horse?
  • When did you first notice this problem?
  • How large is it?
  • Does the bump appear to be causing the horse pain or discomfort?
  • Is there heat or additional swelling in the area?
  • Where, precisely is it?
  • Is it firm or soft?
  • What are the results of the Whole Horse Exam (WHE)?

Diagnoses Your Vet May Consider

The cause of the problem. These are conditions or ailments that are the cause of the observations you make.

Very Common
Less Common
more diagnoses

Author: Doug Thal DVM Dipl. ABVP