Papillomas, Lipomas, Cysts, and Basal Cell Tumors in Dogs

Skin tumors are common in dogs. It is often impossible to determine whether a skin tumor is benign or malignant by appearance alone. The only conclusive way to make a diagnosis is by biopsy, a procedure in which tissue or cells are removed by your veterinarian and examined under a microscope by a veterinary pathologist.

For small tumors it is best for your veterinarian to remove the growth and present the entire specimen to the pathologist. For tumors larger than 1 inch (2.5 cm) across, it may be advisable for your veterinarian to obtain a tissue sample by fine needle aspiration. In this procedure, a needle connected to a syringe is inserted into the tumor and cells are obtained by pulling back on the plunger. Alternatively, the vet can use a cutting needle to obtain a core sample. An open biopsy, in which an incision is made, is preferred for suspected sarcomas and tumors that present diagnostic problems for the pathologist.

Skin Papillomas

Skin papillomas are benign wartlike growths that occur on the skin of the body, on the foot pads, and beneath the nails. They are caused by the canine oral papilloma virus and tend to occur in older dogs, especially older Poodles.

Treatment: They do not need to be removed unless they are causing a problem because of their location on the body. Rarely, these will become injured and bleed or get infected. In these cases, removal is recommended.


A hematoma is a blood clot beneath the skin, caused by a blow or contusion. These are not cancers. Large ones may need to be drained. Ear flap hematomas require special attention (see Swollen Pinna).

Calcifying hematomas are hard masses that resemble bone. They tend to occur at fracture sites, and may be found as a bump on the skull of a tall dog who strikes her head on the underside of the dining room table.

Treatment: Calcifying hematomas do not need be removed but may have to be biopsied if there is a question of bone tumor. They are difficult to treat and often recur.

Epidermal Inclusion Cysts (Sebaceous Cysts)

Epidermal inclusion cysts, also called sebaceous cysts, are common surface tumors found anywhere on the body. Kerry Blue Terriers, Schnauzers, Poodles, and spaniels are most often affected. Epidermal inclusion cysts begin when dry secretions block hair follicles, causing an accumulation of hair and sebum (a cheesy material), and the subsequent formation of a cyst.

These cysts produce a dome-shaped swelling up to an inch or more in size beneath the skin, though most are smaller. They can become infected and may need to be surgically drained. This sometimes leads to a cure.

Treatment: Surgical excision is the treatment of choice, although it is not always required.