Cutaneous Hemangiosarcoma in Dogs: Signs, Staging, and Treatment Options

By Emiel Maddens · Reviewed in consultation with licensed veterinary professionals · Updated August 2026 · 9 min read

What Is Cutaneous Hemangiosarcoma in Dogs?

Cutaneous hemangiosarcoma is a malignant cancer that arises from the endothelial cells lining blood vessels in the skin, producing firm red, purple, or black lumps. Because these tumors are built from abnormal blood vessels, they are often deeply pigmented and can bleed easily when scratched or bumped.

Veterinarians divide the disease into three depth-based categories that carry very different outlooks. The dermal form sits in the superficial layer of the skin, is most closely tied to sun damage, and has the best prognosis. The subcutaneous (hypodermal) form lies deeper beneath the skin and behaves more aggressively, while the visceral form affects internal organs such as the spleen and heart and is the most dangerous. This article focuses on the cutaneous and subcutaneous forms that owners are most likely to notice as a skin lump.

Hemangiosarcoma accounts for roughly 5 to 7 percent of all canine skin and soft-tissue tumors. Early recognition matters because a small dermal tumor caught and removed early can often be cured, whereas deeper or internal disease is much harder to treat.

What Causes Cutaneous Hemangiosarcoma in Dogs?

The dermal form of cutaneous hemangiosarcoma is caused largely by chronic ultraviolet (sun) exposure, which damages the DNA of vascular endothelial cells and drives them to grow uncontrollably. This is why the tumors so often appear on sparsely haired, lightly pigmented skin that gets direct sun, such as the abdomen, inner thighs, groin, and eyelids.

Certain dogs are far more susceptible. Short-coated, light-skinned breeds including Whippets, Dalmatians, Greyhounds, Pit Bull Terriers, and Beagles are overrepresented, and dogs that sunbathe on their backs expose their least protected skin. Solar-induced tumors are frequently preceded by actinic (sun-damage) changes in the surrounding skin, sometimes with multiple lesions appearing over time.

The deeper subcutaneous and visceral forms are less clearly linked to sunlight and are thought to arise from spontaneous mutations in endothelial cells. Genetics, chronic inflammation, and individual immune factors are all believed to play a role, though no single trigger explains every case.

How Do Veterinarians Diagnose and Stage Hemangiosarcoma?

Veterinarians diagnose cutaneous hemangiosarcoma with a tissue biopsy and confirm the extent of disease through staging tests that check whether the cancer has spread. A visual exam alone cannot distinguish this tumor from a harmless blood blister or bruise, so sampling is essential.

Fine needle aspiration often yields only blood because the tumor is vascular, so a surgical biopsy with histopathology is usually required for a definitive diagnosis and to grade the tumor. If you have found a suspicious lump and want help deciding how urgently to act, our Dog Skin Condition Checker can help you describe the lesion accurately before your appointment.

Once diagnosed, staging typically includes chest radiographs (X-rays) to look for lung spread, abdominal ultrasound to evaluate the spleen and liver, and often an echocardiogram to check the heart, since hemangiosarcoma has a tendency to seed these organs. Bloodwork helps assess overall health and detect internal bleeding. Accurate staging is what separates a potentially curable dermal tumor from more advanced disease that needs systemic treatment.

Signs and Symptoms to Watch For

The most recognizable sign of cutaneous hemangiosarcoma is a red, purple, or black raised lump on the skin, most often on sun-exposed areas. These lesions may look like a blood blister, may ulcerate, and can bleed with minor trauma.

Because the depth of the tumor changes the outlook so dramatically, understanding the differences helps owners gauge urgency:

Treatment Options for Cutaneous Hemangiosarcoma

The cornerstone of treatment for cutaneous hemangiosarcoma is complete surgical removal with wide margins, and for dermal tumors that are fully excised, surgery alone is often curative. The deeper and more advanced the tumor, the more likely additional therapy will be recommended.

For subcutaneous or higher-grade tumors, or when cancer cells have spread, veterinary oncologists may add chemotherapy (commonly doxorubicin-based protocols) to slow progression and extend survival. Radiation therapy is sometimes used when complete surgical removal is not possible. Because surgical incisions and any ulcerated, bleeding tumor surfaces are vulnerable to secondary bacterial infection, keeping these areas clean is an important part of recovery.

An antiseptic cleanser can support post-surgical skin hygiene under your veterinarian's guidance. Chlorhexidine Shampoo contains 2 percent chlorhexidine gluconate, which disrupts the cell membranes of Staphylococcus and other surface bacteria that can colonize compromised skin, helping reduce infection risk around healing incision sites. Use it only on intact skin around the wound and never directly on an open surgical incision unless your veterinarian advises it. For more on healing after skin surgery, see our guides on why senior dogs heal slower and age-related immune decline and recurrent skin infections, and review our overview of chlorhexidine for dogs.

Prevention and Long-Term Management

Because ultraviolet light is the leading driver of dermal hemangiosarcoma, sun protection is the single most effective prevention strategy for at-risk dogs. Limiting midday sun, providing shade, and using pet-safe sunscreen or UV-blocking garments on light, thinly haired skin can meaningfully lower risk in vulnerable breeds.

For dogs that have already been treated, long-term management centers on vigilant monitoring for new lesions and signs of recurrence. Owners should perform regular skin checks, photograph any spots for comparison, and keep scheduled oncology rechecks that may include repeat imaging to catch internal spread early. Prompt removal of new dermal tumors keeps the prognosis favorable.

Quality of life remains the priority throughout. Dogs treated for localized dermal disease frequently do very well and return to normal activity, while those with deeper or internal involvement benefit from a coordinated plan that balances cancer control with comfort. Early detection, consistent sun protection, and good wound hygiene together give affected dogs the best possible outcome.

Frequently Asked Questions

Is cutaneous hemangiosarcoma in dogs curable?

The dermal (skin-surface) form can often be cured when it is completely removed with surgery before it spreads. Deeper subcutaneous and internal forms are more aggressive and usually require additional treatment such as chemotherapy, with a more guarded prognosis.

What does hemangiosarcoma look like on a dog's skin?

It typically appears as a firm red, purple, or black raised lump or plaque, often on sparsely haired, sun-exposed skin like the belly and inner thighs. The lesions may look like a blood blister and can bleed easily with minor trauma.

Does sun exposure cause hemangiosarcoma in dogs?

Yes, for the dermal form. Chronic ultraviolet exposure damages the blood-vessel lining cells and is the leading cause of skin-surface hemangiosarcoma, especially in short-coated, light-skinned breeds. Sun protection is the best prevention for at-risk dogs.

How is hemangiosarcoma diagnosed in dogs?

A surgical biopsy with histopathology is usually needed because the tumor is vascular and fine needle aspirates often yield only blood. Staging with chest X-rays, abdominal ultrasound, and often an echocardiogram determines whether the cancer has spread.

Which dog breeds are most at risk for cutaneous hemangiosarcoma?

Short-coated, lightly pigmented breeds are overrepresented, including Whippets, Dalmatians, Greyhounds, Pit Bull Terriers, and Beagles. Dogs that sunbathe on their backs are especially prone to tumors on the exposed abdomen.

Sources

1. Withrow SJ, Vail DM, Page RL. Withrow and MacEwen's Small Animal Clinical Oncology. 5th ed. Elsevier Saunders; 2013:679-688.
2. Ward H, Fox LE, Calderwood-Mays MB, et al. Cutaneous hemangiosarcoma in 25 dogs: a retrospective study. Journal of Veterinary Internal Medicine. 1994;8(5):345-348.
3. Szivek A, Burns RE, Gericota B, et al. Clinical outcome in 94 cases of dermal haemangiosarcoma in dogs treated with surgical excision. Veterinary and Comparative Oncology. 2012;10(1):65-73.
4. Nikula KJ, Benjamin SA, Angleton GM, et al. Ultraviolet radiation, solar dermatosis, and cutaneous neoplasia in dogs. Radiation Research. 1992;129(1):11-18.

Related Reading

• Why Senior Dogs Heal Slower: Age-Related Wound Recovery Explained
• Age-Related Immune Decline and Recurrent Skin Infections in Senior Dogs
• Thin Fragile Skin in Elderly Dogs: Causes, Protection, and Daily Care

Emiel Maddens

Founder of Vetified. Develops topical antifungal and antimicrobial formulations for companion animals. Vetified products are listed on DailyMed and manufactured through FDA-registered facilities in the United States.

Veterinary review: All Vetified content is developed in consultation with licensed veterinary professionals and references peer-reviewed research published in journals including Veterinary Dermatology, JAVMA, and Journal of Small Animal Practice.