Haemangiosarcoma in Dogs: Signs, Causes & Treatment Guide

Haemangiosarcoma is a highly aggressive cancer affecting the cells that line a dog's blood vessels. This malignant tumour can develop in any part of the dog's body where blood vessels are present but most frequently occurs in the spleen, heart, skin, liver, and soft tissues. Due to its blood-filled nature, tumours are fragile and prone to rupture, potentially causing severe internal bleeding and life-threatening emergencies.

Understanding this disease is crucial for responsible dog owners, especially those with breeds predisposed to developing haemangiosarcoma. Early detection can make a significant difference, though the prognosis is often challenging.

Common Locations and Breed Risk

Haemangiosarcoma can appear anywhere blood vessels exist, but it most commonly affects:

• The spleen — the most common site for initial tumour development
• The heart, particularly the right atrium
• The skin, especially in lightly haired or sun-exposed areas
• The liver
• Soft tissues beneath the skin (subcutaneous tissue)

Several breeds have a higher risk of developing haemangiosarcoma, often linked to genetic susceptibility. Medium to large breeds between six and thirteen years old are most commonly affected. High-risk breeds include:

• German Shepherd puppies
• Golden Retriever puppies
• Labrador Retriever puppies
• Boxers
• Dobermanns
• English Setters

Responsible breeding practices are vital to reduce genetic risks and improve breed health over time.

Types of Haemangiosarcoma

Dermal Haemangiosarcoma

This type affects the skin and is often linked to prolonged sun exposure. Tumours usually form on sparsely haired body parts such as the abdomen or any area with white hair. It can appear as a red or black skin growth:

• Look for unusual lumps or patches of red or darkened skin, which may bleed if scratched

This form has a better prognosis as the tumours can often be surgically removed, and dogs may recover well with prompt treatment. Breeds commonly affected are Dalmatians, German Shepherds, and Pit Bull Terriers (noting that Pit Bulls are banned in the UK, so ensuring compliance with local regulations is essential).

Subcutaneous (Hypodermal) Haemangiosarcoma

Here, the tumour develops beneath normal-looking skin, often appearing as a dark red mass under the skin surface. This type tends to spread quickly to internal organs, leading to a poorer prognosis.

Visceral Haemangiosarcoma

This invasive cancer mainly affects internal organs such as the spleen and heart:

• Spleen: The spleen is a critical blood-filtering organ. Tumour rupture here can cause sudden internal bleeding. Surgical removal (splenectomy) might be necessary but does not guarantee stopping cancer spread.
• Heart: Tumours in the heart can cause pericardial effusion—fluid accumulation around the heart sac—impairing heart function and causing collapse.

Unfortunately, visceral haemangiosarcoma carries a very guarded prognosis due to its aggressive nature.

Signs and Symptoms

Because haemangiosarcoma often develops internally, symptoms can be subtle or absent until the disease is advanced or a tumour ruptures. Owners should watch for:

• Lumps under the skin
• Pale gums or weakness
• Sudden collapse or lethargy
• Swollen abdomen or difficulty breathing
• Unexplained bleeding such as nosebleeds
• Seizures or abnormal heart rhythms

If your dog shows any sudden signs of illness, especially collapse, seek emergency veterinary care immediately.

Diagnosis

Diagnosing haemangiosarcoma can be complex due to non-specific early symptoms. Vets typically use a combination of medical history, physical examination, and diagnostic tests such as:

• Blood tests to check for anaemia and clotting issues
• Ultrasound and X-rays to detect internal tumours and bleeding
• Aspirating belly fluid to check for blood
• Biopsy of accessible tumours (though challenging)

Early vet care and diagnostic imaging can improve chances of timely diagnosis.

Treatment Options

Treatment depends on tumour location and spread:

• Dermal tumours: Surgical removal is often effective.
• Internal tumours: Emergency surgery (e.g., splenectomy) may stop bleeding. Chemotherapy is commonly used afterward to delay progression, though it is not curative.
• Radiotherapy may be considered for some dermal or subcutaneous tumours.

Veterinary oncologists can tailor treatment plans, balancing quality of life and therapy side effects.

Prognosis and Aftercare

Sadly, haemangiosarcoma has a poor prognosis overall. Dogs with internal tumours often survive just a few months after diagnosis even with surgery and chemotherapy. Those with dermal haemangiosarcoma generally have a better outlook, often living six months or longer post-surgery.

Owners can support their dogs by providing comfortable, supportive care, monitoring for symptom changes, and maintaining close communication with their vet.

Preventive Measures

While the exact causes of visceral haemangiosarcoma remain unclear, some prevention tips include:

• Protecting dogs from excessive sun exposure, especially at-risk breeds, to lower dermal haemangiosarcoma risk
• Choosing reputable breeders who screen for genetic diseases
• Regular veterinary check-ups for early detection

Being attentive to your dog's health and changes in behaviour is always the best practice.

Conclusion

Haemangiosarcoma in dogs is an aggressive cancer that requires prompt veterinary attention. Responsible ownership, including selecting dogs from reputable breeders, protecting at-risk breeds from sun damage, and seeking early vet intervention at signs of illness, can improve quality of life. If diagnosed early, some treatment options may prolong survival and comfort. Always work closely with your vet to choose the best care for your beloved companion.