Skin Cancer in Dogs

Overview of skin cancers including mast cell tumours, melanoma, squamous cell carcinoma, and cutaneous hemangiosarcoma.

What is Skin Cancer in Dogs?

Skin tumours are the single most common cancer group in dogs, and appearance alone cannot distinguish benign from malignant. Any new lump — or an existing lump that changes in size, colour, or texture — deserves a fine-needle aspirate. Most skin cancers are curable when caught early and surgically removed with clean margins.

Common signs and symptoms

Signs vary between dogs and can be subtle at first. Watch for the following, especially if several appear together or persist for more than a few days:

  • New or growing lump on or under the skin
  • Changes in colour, ulceration, or bleeding
  • Lumps that fluctuate in size (classic for mast cell tumours)
  • Sores that won't heal, especially on lightly pigmented skin
  • Lumps on the nail bed or between toes

Risk factors

Certain dogs are more predisposed. Understanding risk helps you screen earlier and act sooner.

  • Age 7+
  • Boxer, Bulldog, Pug, Golden Retriever, Labrador (mast cell tumours)
  • White or lightly pigmented dogs with sun exposure (squamous cell carcinoma)
  • Scottish Terrier, Standard Poodle (melanoma)

When to see a vet

Use this as general triage guidance, not a substitute for veterinary advice.

  • Book a routine appointment if: you find any new lump — even small ones. A quick needle aspirate is the fastest way to know what you're dealing with.
  • Seek urgent care if: a lump is ulcerating, bleeding heavily, or growing rapidly.

Diagnosis and management

Diagnosis begins with fine-needle aspiration and cytology; biopsy provides grade. Treatment is usually surgical excision with appropriate margins, sometimes followed by radiation or chemotherapy depending on grade and staging. Data referenced from the Veterinary Society of Surgical Oncology (VSSO).

Mast Cell Tumours (skin)

The most common skin cancer in dogs. Behaviour ranges from benign (low grade) to highly aggressive (high grade). Boxers, Bulldogs, and Pugs are overrepresented. Grade guides prognosis and treatment; wide surgical margins are the cornerstone of low-grade cases.

Cutaneous Melanoma

Skin melanomas are usually benign in dogs, in contrast to oral or nail-bed melanomas which behave aggressively. Any pigmented lesion that changes should still be evaluated.

Squamous Cell Carcinoma

Common in lightly pigmented, sun-exposed skin (belly, nose, ear tips) and in the nail bed. Locally aggressive but slower to metastasise than many other cancers.

Cutaneous Hemangiosarcoma

The 'good' hemangiosarcoma: when limited to the skin (not deeper tissues), surgical removal is often curative. Sun exposure is a risk factor in short-coated, light-skinned dogs.

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