Canine Cysts

A cyst is a fluid-filled closed cavity or sac that is lined by an epithelium. Cysts can be of normal, abnormal, non-cancerous, or cancerous tissues. Sebaceous cysts are derived from sebaceous (oil-secreting) glands, apocrine cysts are derived from sweat glands. Cysts may burst or discharge to the surface via a fistula or sinus. They may be congenital or developmental.1

Sebaceous cysts develop within the skin of dogs when sebum normally formed within sebaceous glands is not allowed to escape. These cysts can develop in multiple locations on a dog's body. There is a breed predisposition for this condition as cocker spaniels, springer spaniels, terriers, and shepherds are most often affected.2

Apocrine cysts are well-defined, firm or soft nodules ranging from several millimeters to several centimeters in diameter. The masses often have a blue tint when viewed through the overlying skin with thinning hair. Cyst content is usually clear and watery, but may be brown and gelatinous. Affected dogs are most commonly 6 years of age or older.3 The majority of skin cysts in cats and dogs are follicular in origin. They appear as round, smooth, firm to touch lumps.

Cocker spaniels

The typical first step in evaluating a cystic mass is to perform fine-needle aspiration to obtain material for cytologic evaluation. Using this simple, relatively non-traumatic, quick, and inexpensive procedure, a veterinarian can make a definitive diagnosis of the nature of the mass in most dogs. If a cytological diagnosis of a non-cancerous (benign) tumor is made, the veterinarian may recommend the removal of a cyst since there is always a risk of bacterial infection.4


  1. O. M. Radostits, Ian G. Mayhew, Doreen Marie Houston. Veterinary clinical examination and diagnosis
  2. Chris C. Pinney. The Complete Home Veterinary Guide
  3. Thelma Lee Gross. Skin diseases of the dog and cat: clinical and histopathologic diagnosis
  4. Richard W. Nelson, C. Guillermo Couto. Small Animal Internal Medicine



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