Diagnosing Skin Tumors in Dogs

Skin tumors in dogs may be of several types. These growths may be benign or malignant. The tumors may be papillomas, sebaceous adenomas, fatty tumors, melanomas, mast cell tumors and other types. The diagnosis of the skin tumors may be done judging by the appearance of the tumor and by performing a biopsy.

Types of Canine Tumors

The main types of canine skin tumors include:

  • Epithelial tumors such as papillomas, squamous cell carcinomas, basal cell carcinomas, hair follicle tumors, sebaceous gland tumors and aporcine gland tumors
  • Soft tissue sarcomas, with mesenchymal origin
  • Round cell tumors including mast cell tumors, lymphomas or plasmacytoma
  • Melanomas

Among these, papillomas, sebaceous gland tumors, mast cell tumors and lipomas are the most frequent in dogs.


Papillomas are benign tumors and may be found on the skin or in the mouth of the dog. The papilloma is caused by a virus and is contagious. Papillomas are more common in younger canines. The papillomas, also known as warts have the appearance of round lesions; the surface of the tumor may be rough and there tend to be several warts in one place.

In rare cases, the papillomas may turn into cancerous tumors or squamous cell carcinomas.

Sebaceous Gland Tumors

The sebaceous gland tumors may be of various types including:

  • Nodular sebaceous tumors
  • Epithelioma
  • Sebaceous adenomas

These are all benign tumors that have the appearance of cauliflower and they may be small or larger (up to a few centimeters); these warts like tumors are firm and raised. These tumors may be dark, yellow or pink and there may be hair loss around these tumors.

The sebaceous adenocarcinomas are malignant and are red, ulcerated and solid. These carcinomas may bleed.

Mast Cell Tumors

Mast cell tumors are malignant growths that are the most frequently met tumors in canines. The tumors may be firm or softer and may have indentations or be smooth; the tumor may often bleed and will affect mostly older dogs. Some dog breeds are more susceptible to developing these mast cell tumors.


Lipomas are tumors that are made up of fatty cells and typically form under the skin. Lipomas are benign growths that may be soft or firmer and will be bound to the dog's muscles or tendons.

Detecting Skin Tumors

When you groom your pet, you should always look out for abnormalities, lumps, bumps, sores and skin growths. Don't forget to check the lips, eye lids, ears or other more hidden areas where tumors may grow.

Notify your vet when you find a suspicious tumor.


The biopsy is the only test that can give conclusive results in regards to the skin tumor. The test will establish the type of cells that make up the tumor and whether the tumor is benign or malignant.

The vet may perform other tests (blood tests, x-rays or ultrasounds) to see if the tumor has extended.