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Squamous Cell Carcinoma

Squamous cell carcinoma is a frequently diagnosed cancer in dogs that may occur in many different locations. Cutaneous squamous cell carcinomas occur in older dogs, and lesions commonly form on the head, paws, abdomen and perineum. On white-skinned, short-haired breeds these tumors usually develop on the abdomen, genitals and groin. Most cutaneous squamous cell carcinomas appear as firm, raised, frequently ulcerated bumps; sometimes they protrude from the skin and resemble a wart.

Squamous cell carcinomas may also occur within the oral cavity of elderly dogs.  These masses are often invasive to adjacent tissue, including bone, but uncommonly metastasize to the regional lymph node. A tumor that originates in the tonsil will grow rapidly and spread to surrounding tissue and to regional lymph nodes as well as metastasize to the lungs.

Subungual (toenail bed) squamous cell carcinomas generally occur in dark-coated dogs on the paws. Females have a slightly higher rate of occurrence, and both the forelimbs and hind limbs are equally predisposed to tumor development.


  • Shallow sore on the skin with a crust over the top
  •  Deep raw sore on the skin or in the mouth
  • Raised red area on teh skin or in the mouth
  • Cauliflower-shaped growth

Breeds at Risk

  • Basset Hounds
  • Dalmations
  • Beagles
  • Gordon Setters
  • Bloodhounds
  • Kerry Blue Terriers
  • Briards
  • Schnauzers
  • Bull Terriers
  • Standard Poodles


Your veterinarian may perform cytology studies to look at the cells making up the tumor. This is done by collecting cells from the area with a needle or by pressing a slide or other object directly on top of the area to collect the cells. Preferably, part or all of the tumor should be removed for biopsy to accurately diagnose squamous cell carcinoma. Biopsy allows a close examination of the architecture and cell makeup of the tumor under a microscope using specialized techniques to determine the degree of malignancy.

To determine the stage of the cancer, your veterinarian will likely need to run additional tests, which may include blood testing, urinalysis and radiography of the chest and abdomen. Your pet’s lymph nodes will also need to be examined to see if the tumor has spread.


Surgical removal of the squamous cell carcinoma is the treatment of choice, but removal of the entire tumor may not always be possible because of its size or location. In this case, additional treatment may include the following:

  • Radiation therapy
  • Plesiotherapy (topical application of a radiation source to the area of the cancer) if the tumor is very small
  • Cryotherapy (application of extreme cold to the area of the lesion)
  • Photodynamic therapy (administration of a medication that photosensitizes the area of the cancer and results in death of cancer cells)
  • Chemotherapy


Skin carcinomas are generally local in nature but may metastasize. Digital, nail-bed tumors may recur in the same digit or in another after several months or years. About one-third of tumors in this area will metastasize after the digit is amputated because these tumors can spread through the lymphatic vessels.

Prognosis for oral squamous cell carcinoma entirely depends on the location of the tumor and metastatic rate. Tumors that are surgically accessible and have a wide margin may be controlled for a long time. Inaccessible tumors or tumors that have spread to other areas may be controlled by radiation therapy, chemotherapy or a combination. 

Current Research

Click here to find out about Morris Animal Foundation--funded research into squamous cell carcinoma.

Morris Animal Foundation urges pet owners not to implement any suggestions on animal health treatments without prior consultation with their licensed veterinarian. If your pet is experiencing health issues, contact your licensed veterinarian. The Foundation funds research to enhance medical options available to veterinary professionals and their patients.