Black blood-filled bump on a dog. Is it Hemangiosarcoma?

There’s no doubt that dogs are a man’s best friend. Unlike humans, their feelings are always genuine and their love unconditional. Indeed, many people prefer the company of dogs to actual humans for these reasons. To repay their loyalty, it’s only natural you want to provide them with only the best. You became so frightened when you noticed unsightly black lumps covering your dog’s skin.

Is it deadly cancer or an innocent wart? Can your dog recover from cancer, or will you have to resort to drastic measures? Read on to find out.

What is cancer?

dog bed with dog in it

Understanding cancer and its forms might make you realize how severe it can be.

Like other organisms, dogs’ bodies are made of billions of cells. In a healthy body, these cells die and regrow continuously. The information which regulates this cycle is encoded in the form of DNA.

The issue arises when something damages the DNA. As a result, a cell will begin to grow and split endlessly. Over time, it will reproduce into a large cluster of sick cells – called tumors. They are dangerous because they spread rapidly and envelop healthy tissue. In time, they can lead to organ failures.

Factors that contribute to cancer formation

While no one can accurately predict if your dog will develop this frightening disease or not, some factors facilitate its growth.

All these factors stem from DNA damage. Since the genetic information is passed down from the parents to their child, your puppy might have simply inherited this predisposition. Though some breeds are more at risk than others, you can’t do much about it.

Radiation also promotes tumor formation. You might think this doesn’t concern you, but you and your canine companion are exposed to this factor daily. In addition to visible light, sun rays also contain UV light. This high-energy light damages DNA and may lead to cell proliferation. Though you probably know to stay out of direct sunlight yourself, your furry friends are also at risk. It’s especially if you own a short-haired breed.

Mutations accumulate as your pets grow older. Because they now live longer than they used to in the past, they’re much more susceptible to cancer.

Certain chemicals play a part as well. Some research suggests that tobacco from smoke might cause your dog to develop cancer. However, there’s not much evidence for these claims.

There’s a black, bleeding lump on my dog.

If you find black bleeding lumps on your dog’s skin, there’s a high probability he has skin cancer. However, some of the forms can be benign (they don’t spread), and a majority of them are not. Left unchecked, skin tumors can be fatal. Thus, you should take your pet to the vet right away. Early diagnosis can determine how the rest of your canine’s life plays out. 

How is dog cancer diagnosed?

happy dog

Here are some of the most common methods used to diagnose this disease.

Blood count test

This test measures the blood cells. If your pet has cancer, their level increases.

Blood serum test

This test is important to detect whether the liver and kidneys function properly.

Urine test

urine test or urinalysis can detect cancer cells in your pet’s urine.

Chest X-rays

Checks the state of the heart and lungs.

Abdominal ultrasound

Abdominal ultrasound can detect anomalies in internal organs.

Hemangiosarcoma in dogs

Hemangiosarcoma is arguably the most dangerous type of dog cancer. It stems from epithelial cells which cover the inner side of blood vessels. Because veins and arteries spread across the whole body, these vascular tumors might settle anywhere. Though they appear mostly as lumps on your puppy’s skin, they can also affect internal organs. The most common ones are the liver, heart, and spleen.

This form is most prevalent in breeds such as Golden Retrievers, German Shepherds, and Labradors.

Hemangiosarcoma tumors appear as lumps or ulcers on your dog’s skin. They might often bleed. Internal vascular tumors are, therefore, much more dangerous. Even though you won’t be able to see the bleeding, it doesn’t mean there isn’t any. The ulcers might burst too. It leads to life-threatening blood loss.

In addition to the visible bumps, your dog might also exhibit symptoms akin to blood loss. Dogs suffering from vascular tumors are often lethargic and weak. Other common signs are pale gums and a swollen belly.

Regrettably, the prognosis for canines with vascular tumors is often heartbreaking. Most won’t survive past one year after the treatment. However, it depends on how early on you spotted the Hemangiosarcoma.

Other types of dog cancer

While Hemangiosarcoma is a vicious disease, it is only one of many types of cancer. As a responsible dog owner, you should at least know these 6 other common types that might plague your pet.


Melanoma is a type of cancer that affects melanocytes. These are pigment cells found in your dog’s skin, where they absorb dangerous UV light.

They appear as dark-colored spots on your canine’s skin. Fortunately, your vet can simply remove these tumors. In most cases, this will be enough to cure your dog.

However, Melanoma can sometimes be malignant. If you see dark spots on your pet’s mouth or eyes, take him to the vet immediately. It is where this type of cancer is most dangerous.


Osteosarcoma plagues mainly larger breeds. This type of tumor grows from bone tissue, mostly in leg bones. An extremely aggressive form of cancer, early symptoms include painful joints and fatigue. If your puppy refuses to walk, it might be due to this searing pain. As the tumor develops, it will manifest as a swollen lump on one of your dog’s legs. It’s often red and feels warmer than usual when you touch it.

Osteosarcoma is often treated by amputating the affected limb. Like any form of cancer, it’s best to nip it in the bud to avoid this drastic procedure.

Because it is often malignant, your dog might have to undergo additional treatments.

Lung Cancer

Lung cancer typically occurs in older dogs past 10 years old. Many times, your dog might not exhibit any symptoms. It makes diagnosing it challenging. It is only after your vet performs an X-ray diagnosis that this disease comes to light.

Despite this, older canines might show signs of lung cancer in time. In addition to breathing difficulties, your pet might refuse to eat. Frequent fatigue and fever are often common.

Surgical removal is often enough to bring back the smile on your dog’s face. However, he might need chemotherapy if the tumors were malignant.

Mammary cancer

Mammary cancer affects mostly female dogs. It’s especially prevalent in un-spayed females. This form may also afflict male dogs, though it’s considered rare.

At first, there are little to no symptoms. These tumors typically manifest as lumps near mammary glands. You’re most likely to notice them if your little one enjoys a good belly rub. As they grow in size, the dog may begin to lick them.

Treatment varies depending on the type. Your vet can remove benign tumors surgically. For malign ones, radiation or chemotherapy might have to follow.

Mast cell cancer

Mast cell tumors (further only MCTs) are another form of skin cancer. They comprise up to 20 % of skin cancer cases. Sadly, MCTs are often malignant.

As they form, mass lesions will appear on your dog’s skin. These lesions are red and might contain fluids. Their size can vary greatly.

Your pet’s lymph nodes might also swell. Loss of appetite and frequent vomiting is also common.

Once more, surgery will usually do the trick. If you detected the MCTs too late, your canine would also have to undergo chemotherapy.


Lymphoma is any form of cancer affecting lymphocytes (white blood cells). Because there are so many subtypes, it’s difficult to list all the symptoms in a single article. This form generally affects mostly the lymph nodes, spleen, and bone marrow.

The treatment usually calls for chemotherapy. Because white blood cells flow freely in the blood, it makes sense that you can’t remove them surgically. Still, surgery might sometimes be necessary if cancer spreads to other organs.

Most aggressive dog cancer

small dog

What makes tumors dangerous is their ability to spread. Thus, malignant forms are the most aggressive ones out there.

Based on this, Hemangiosarcoma can be ranked as the most aggressive type. Since vascular tumors can travel anywhere via blood, they can quickly spread over your poor dog’s body. Because they can cause internal bleeding, they can be lethal if found too late.

Osteosarcoma is quite aggressive as well. Not only is it excruciatingly painful for your poor dog, but it also spreads across the body. Often, your canine will have to undergo amputation to treat it. And even then, his life span will be shortened. Larger breeds are more susceptible to this type.

Finally, lymphoma is often malignant too. Since these tumors are derived from white blood cells, they can reach most body parts. For this reason, it’s difficult to treat.

What do cancer sores look like on a dog?

Most cancer sores look like pigmented, swollen lumps. Depending on the type, they might be ulcerated. These sores can be black, pink, or red. They might also bleed.

Look for them, especially in hairless areas such as the abdomen. That’s where they grow most often.

Dog skin cancer or wart

Unlike tumors, warts are caused by papillomavirus. They often disappear on their own after a few months unless your pet has immunity issues. Warts aren’t dangerous unless they grow in the wrong spots. If they sprout on your canine’s paws, he might have problems with walking. They might also be a nuisance near the mouth and eyes.

If warts don’t disappear on their own, they can be removed surgically. Contrary to tumors, they don’t ulcerate or bleed. Warts resemble a cauliflower in texture and are often pale pink.

Skin tumors appear as black bumps that may be ulcerated. In severe cases, they might also bleed. Generally larger than warts, they rarely go away on their own. Skin tumors are dangerous, and you should deal with them without delay.

If you can’t tell them apart, take your loyal companion to the vet. Better safe than sorry.

Is Hemangiosarcoma a malignant form of cancer?

Unfortunately, Hemangiosarcoma is malignant and thus one of the most dangerous types of dog cancer.

When researching cancer, you may have stumbled upon the term metastasis. It refers to cancer spreading across the entire body.

Hemangiosarcoma tumors develop on the inner side of blood vessels. It’s incredibly easy for some of the diseased cells to ‘break off’ and fall into the bloodstream. The blood can then carry them across the entire body of the poor canine. When some of these cells settle, new tumors will appear elsewhere.

Signs a dog is dying of cancer

Cancer invades the body and will begin to shut down vital organs. Lungs are one such organ. When the tumors spread, your dog won’t be able to breathe properly. His breaths can be either too short and shallow or too lengthy and strained.

Loss of appetite is another sign that this disease has become too severe. It leads to a lack of energy. As a result, your canine companion might refuse to play or even go for a walk.

Moreover, canines suffering from cancer can’t poop or pee properly. While you can expect puppies to pee a lot everywhere, mature dogs should have more control of this basic need. However, this disease often leads to incontinence. In some cases, dying pets won’t be able to even move from their waste.

Diarrhea, constipation, and vomiting often occur in the later stages of cancer.

As the pain becomes more pronounced, your canine might be unable to fall asleep.

Lastly, he might vocalize his agony through howling and whining.

Stages of dog cancer leading to death

During the early stages of dog cancer, your furry friend will lose his appetite. Diarrhea, vomiting, and frequent urination might also accompany this symptom. Constant fatigue then follows. Your pet might also start losing hair.

As for physical signs, you may notice lumps covering your canine’s skin. You should also check his lymph nodes. You can feel them where the jaw meets the neck and under the front armpits. Enlarged lymph nodes are a reason for concern. Pale gums might point to blood loss resulting from internal bleeding.

When the disease reaches the final stages, these symptoms will worsen. Your pet will eat and drink clumsily and might refuse to altogether. It often results in severe weight loss. The ulcers will spread across the whole body. Because they are painful, he won’t like you touching them and might become aggressive. You can expect seizures and shallow breathing too.

When to euthanize a dog with cancer

Euthanizing your dog should be the last resort. Though we don’t wish this difficult choice on anyone, be ready to face it if your dog’s diagnosed with malignant tumors. On the one hand, it might sound cruel and you may wonder if you should give him a fighting chance. On the other hand, this disease can be nightmarishly painful in its last stages. Delivering your best friend from constant pain can be an act of mercy.

So when should you prepare to say your final goodbye?

As an owner, it is your sacred duty to provide your dog with the best quality of life you can. In its final stages, cancer will greatly reduce this quality. No longer will your loyal friend be his happy self. He won’t be able to eat and drink properly, and each breath he draws will be a challenge. He won’t be able to control where he urinates or defecates anymore.

Letting go can be incredibly difficult. But in the end, you’re choosing whether to protect yourself from emotional pain or whether you don’t want your dog to suffer anymore. Keeping him alive only to protect your feelings is selfish. When the time has come to bid the last farewell to your friend, know that he’s going to a better place where he won’t suffer anymore.

Though a vet can offer invaluable counsel when things get this bad, they can’t decide for you. As the owner, the choice is ultimately yours and yours alone.


Is skin cancer fatal in dogs?

There’s no straight answer to this question. Benign tumors pose little to no threat to your canine’s life span once your vet removes them. However, malignant ones can be fatal if ignored or overlooked.

How long will a dog live with a cancerous lump?

It depends on how old the malignant tumor is. If you notice it very early, it won’t cause much harm. However, most people don’t notice cancerous lumps until they have already spread. Untreated, your dog won’t live for more than 3 months. Surgery and chemotherapy can extend the life span up to 2 years.

Does a lump on a dog mean cancer?

Lumps on your canine friend’s skin don’t always point to this dreaded disease. They might simply be warts. Warts are of viral origin, and they are mostly harmless. Some lumps are also benign, and removing them is often enough. Cancerous lumps are hard and red. They tend to ulcerate as well.
If you want to be sure, visit your vet. They can perform the right diagnosis.

When should I worry about a lump on my dog?

It’s always better to be safe than sorry. Take him in whenever you find something unusual you don’t know what is.


To summarize, black bleeding bumps on your dog’s skin can point to skin cancer. Most types are malignant, meaning the tumors spread across the body. Early diagnosis can be the difference between a long healthy life and having to say untimely goodbye to your furry friend. Treatment options include surgery and chemotherapy, depending on the type.

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