Dog Skin: Tumors

Overview: Dog Skin Tumors

There are primarily two types of canine skin tumors, benign and malignant. Benign tumors are usually encapsulated cellular growths, which appear as a lump, or bulge on the skin surface. These are non fatal, easily diagnosed and curable forms of skin tumors. These types of cysts, lumps and bumps are common, which is why it does not pay to panic when you notice a bump on your dog. Skin Adenomas and hidradenomas are some examples of benign tumors in dogs.

Malignant tumors are generally called cancers and grow rapidly. These tumors can be fatal. With the cancerous cells dispersing, diffusing and spreading to other tissues and organs.  They can be cured if caught early and removed, but can lead to a grave prognosis if surgery, radiation and chemotherapy cannot correct the problem. These may also cause secondary tumors or cancers, like that of lymphatic and circulatory system tumors. Hemangiosarcomas, Mast cell tumors and squamous cell carcinomas are some examples of malignant dog cancer tumors.

Dog Skin Tumor

Types of Dog Skin Lumps and Bumps

Dog Skin Cancer Tumors (Malignant)

Different forms of canine skin tumors may occur. These are highly variable in their appearance, signs, onset and mode of activity. They are either benign or malignant, depending upon the nature of cell activity. It is estimated that the number of reported cases for dog tumors has significantly increased in recent years due to increased exposure to environmental pre disposing factors, awareness amongst dog owners and different carcinogens.

Malignant Dog Skin Tumor on Paw

  • Histiocytoma; Histiocytomas are benign tumors, which appear as bumps on the ear, head and limbs. These are not painful, but may get ulcerated in latter stages. More than 50% of the dog population in the United States is susceptible for this type of dog skin tumor which originates from Langerharns cells.

  • Hemangiosarcoma; Hemangiosarcomas are malignant tumors, in dogs they may appear at the limbs, prepuce (skin that covers the clitoris) and abdomen. This form may appear at the skin surface and beneath the skin (Sub Cutaneous). Hemangiosarcomas are seen firm, raised and dark nodular structures at the skin surface and as rapidly growing nodules beneath they skin. They may appear as an injury or a wound, and may bleed excessively.

  • Mast Cell Tumors; Mast cells tumors are usually caused by histaminic secretions (fluid released by cells) in the dog’s body. Mast cell neoplasia of the internal organs and lymphatic system may also cause a neoplastic activity on the skin. The skin surface may appear as inflamed, allergic or appear as if it was bitten by an insect. Involvement of the lymph nodes on the lateral sides of the dog’s body helps in diagnosis.

  • Melanocytic Tumors; These may be benign or malignant, and involve the melanin or skin pigment producing cells, called melanocytes. The skin may appear rough, darkened and look like it has progressively degenerated (looks less healthy). These may appear anywhere on the body and may involve other parts of body like the lymphatic system, respiratory system and frequently the renal system (kidneys). Pigmented or non pigmented, solitary masses are revealed on physical palpation (touching) of the skin.

  • Squamous Cell Carcinomas; Malignant tumor of skin tissues, suspected for those dogs having erosive lesions on the skin which remain incurable even after months of treatment. The exact cause of these dog skin tumors is unknown, but more cases occur in sunny climates, therefore it is suspected that squamous cell carcinoma is caused by radiation. This type of tumor spreads easily, and can affect the lymph nodes and the muscoskeletal system.

Benign (not cancer) Dog Skin Growths, Lumps and Bumps

Benign skin growths are not a long-term health threat. That doesn't mean that they cannot be quite large, with some growing to the size of a basketball (in the case of a large lipoma). These types of dog skin tumors do not spread to adjacent tissue or other organs.  There can be several benign dog skin growths on a dog at the same time and usually do not require any treatment.

Common types include:

  • Cysts: dog skin cysts are pea-sized skin-covered sacs filled with a thick liquid.

  • Warts: Warts are caused by a viral infection and are hard and have a rough-surface. 

  • Lipomas: A lipoma is a collection of soft fatty tissue that forms just under the skin surface. These growths are usually the size of a quarter. If a lipoma develops in a way that interferes with the way a dog walks, it might need to be removed. Some owners opt to remove large lipomas for cosmetic reasons. Lipomas are relatively easy to remove.

  • Adenoma: these types of small  dog skin tumors develop in the sebaceous glands which are mostly at the base of the hair follicles. These are frequently seen Cocker spaniels and miniature poodles.  Cancerous forms of adenoma are called adenocarcinomas, which can form in the dog anus tissues.


A needle is inserted into the tumor to draw cells for examination under a microscope.

A veterinarian will take a cell sample from the tumor for examination under a microscope.  Cancer cells have a larger nucleus and less cytoplasm when compared to normal cells.

Dog Skin Tumor Cell Comparison (malignant cells on left, healthy cells on right)


Video: Dog Tumor Lump or Bump Examination, Diagnosis and Treatment

Video of veterinarian describing his approach to dog skin tumor diagnosis and treatment.

A general approach for treating a canine skin tumor involves three options:

  1. Surgical resection is the preferred approach. In different forms of dog skin tumors, the extent of the surgery may differ. In mast cell tumors and squamous cell carcinomas, aggressive and timely surgical resection is required, while the amount of surgery required for a Histiocytoma is very low. Tests for blood type, hemoglobin level and screening are required prior to surgery, along with willingness of the dog owner.

  2. Radiation Therapy is the second most effective way to treat dog skin cancers. X–rays and gamma rays can effectively be used as a primary option for treatment. Radiations is mostly used to eliminate deep malignant tissues, as a secondary option along with a surgical procedure.

  3. Chemotherapy is another option. Anti cancer drugs can be used for this purpose, but have many adverse effects. 

Nutritional supplements such as C-Caps, supportive therapy and other home remedies can only help in restoring physiological condition and possibly provide some level of support, but can never cure a dog skin tumor.

Have A Question About a Dog Skin Problem For Our Editors or Helpful Story to Share?

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