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Your E-Guide to Dog Spleen Tumors 2018

Dog spleen tumors (or splenic masses) often go unnoticed because of their hidden location and vague symptoms.  As with any tumor, they are either benign (non-cancerous) or malignant (cancerous). You might feel as if your dog has something wrong, but you can’t quite put your finger on what it is. In fact, it’s not unusual for people to miss signs and symptoms altogether.  You’re probably wondering if there is a cure, and what treatment options are available. 

Disclaimer:  I am not a veterinarian, nor do I play one on TV.  My goal is to provide accurate, well-researched posts, but human error is always a possibility. Have your dog seen by a veterinarian.

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It can get a little confusing.  To help you, I’ve simplified things so that by the time you’re done reading this post, you will have a better understanding of your dog’s diagnosis and what that means over the long-term.

So let’s get started!

To Understand Dog Spleen Tumors, You Need to Understand the Spleen

In order to understand the different types of dog spleen tumors, it’s important to have a general understanding of the spleen and what it does. The spleen is located next to your dog’s stomach and is one of the body’s vascular organs.  It’s “vascular” because it regulates blood cells and recycles blood protein and iron. In addition, the spleen contains cells that recognize harmful microorganisms in the body.

The spleen has two types of tissue:

Red Pulp Tissue

The activity within the red pulp tissue helps to filter blood (out with the old; in with the new) and recycle the proteins and iron from blood cells. The red pulp connective tissue makes up about 79% of the spleen.  This part of the spleen contains many different blood cells including:

  • Platelet (thrombocytes): These cells promote blood clotting
  • Red Blood Cells – These cells are responsible for delivering oxygen to body tissues

White Pulp Tissue

White pulp tissue contains cells that create an immune response when infection, viruses, or bacteria threaten the body. They constantly protect the body against illness.  White blood cells are created from bone marrow and, because some only last a few days, the bone marrow is constantly making more.

Types of White Blood Cells Include:

-Monocytes (help to break down bacteria)

-Lymphocytes (create antibodies to protection against bacteria, etc.)

-Neutrophils (Kill bacteria and fungi)

-Basophils (these are the alarm-sounders when infectious agents appear)

-Eosinophils (kill parasites, destroy cancer cells, and can also help with allergic reactions within the body)

With so many cells working together, how is it possible for dog spleen tumors to occur?

That is the million dollar question that researchers are trying to figure out.  One of the reasons why there is no cure for dog spleen tumors is because science hasn’t been able to precisely identify the initial trigger that cause the body’s systems to malfunction and allow cancer to grow. The brief description of blood cells, connective tissues, and organs is just a whiff of the details you’d find in a medical textbook. 

Until someone unlocks the mysteries behind cancer, the best our medical professionals can do is attempt early diagnosis.  The only way for a veterinarian to identify whether a tumor on the spleen is malignant or not, is to remove it entirely. Yes, your dog can live without a spleen despite its many functions. The bodies of humans and animals are amazing in that they can (for the most part) engage other organs to pick up the slack.

The sad reality is that dog spleen tumors are often masked by vague symptoms.  If the mass is found cancerous, the fact that he no longer has a spleen is the least of concerns. Hemangiosarcoma (detailed further into the post) is an aggressive cancer that, if found in the removed spleen, has likely already spread to other organs.

Two Characterizations of Spleen Tumors:

Tumors of the spleen are considered either non-lymphoid or lymphoid.  

Lymphoid Tumor

A lymphoid tumor originates in the lymphatic tissue located in the dog’s spleen. They can occur in other areas as well including the lymph nodes (those lumps and bumps that get enlarged when you’re coming down with something) or in the bone marrow.

Lymphoid (cancer of the lymphocytes)

Cancers of the lymphocytes (white blood cells that reside in the white pulp of the spleen) are common in dog spleen tumors. Other cancers of the lymphocytes include: mast cell tumors and leukemia.

You might be interested in this post:

CLICK HERE TO READ:    Mast Cell Tumor Dog Life Expectancy 2018

Unlike visible tumors that are a little easier to identify, tumors of the spleen are hidden from view most of the time.  The only way to catch a problem early is to bring your older dog to the veterinarian for regular checkups.

Non-lymphoid (cancer of the blood vessels)

This category of dog spleen tumors include both the non-cancerous hemangioma (benign) and the cancerous hemangiosarcoma (malignant).  How will you remember that?  Just remember that any word that ends in sarcoma signifies cancer. Sarcomas are cancers from the connective tissues of the body including bone, cartilage, fat, nerve.

Hemangiosarcoma (non-lymphoid)

This is probably the cancer your dog has been diagnosed with. Hemangiosarcomas are malignant cancers that develop in blood vessel lining. It can be found in any organ; however, with dogs they tend to appear in the spleen.  It’s only been in recent years (beginning approximately 2015) that researchers have been able to develop more solid theories.  According to Veterinary Sciences (2015; Dec: 2(4): 388-405.) new data suggest “a pluripotent bone marrow progenitor as the cell of origin for this disease.” 

That’s nice.  But what does it mean? 

The Immediate Danger of Hemangiosarcoma

Unfortunately, cancer on the spleen isn’t typically noticed until it becomes enlarged, and even then only a medical professional knows what to feel for. The veterinarian might notice the enlargement during a physical examination, but for you or me, the dog owners, we’re probably going to miss it. 

Hemangiosarcomas are tumors that begin in the lining of blood vessels.  It’s essentially a big mass lodged onto a vascular organ.  Since it’s vascular in nature (meaning it relates to the blood vessels), a lot of blood passes through and accumulates.  The bigger it grows, the greater the chance of a rupture causing a dangerous internal bleed. Most times this is fatal.

Symptoms You Could Easily Miss

Dog spleen tumors like hemangiosarcoma are aggressive and can quickly spread to other parts of the body.  Veterinarians discover these tumors after the dog’s owners bring the dog in some other concern.  Other times, it might be suspected during a routine exam. Unfortunately, that’s not always the case.  It’s nobody’s “fault”. The reality is that this type of cancer likes to hide and is really tricky to spot.

Vague symptoms (if any) include signs of weakness, swollen belly, the skin might bruise, and the dog could have pale gums.  In this case, pale gums would likely point to anemia.  Sadly, tumors of the spleen can rupture suddenly, leaving the dog in critical condition. Rarely, the blood is reabsorbed into the abdomen and the dog’s body manages to take care of the internal bleed.  It seems, however, the most likely case with an internal bleed from this type of rupture is very dire. 

Older dogs should have yearly checkups (or more if you suspect something) as a means to detect dog spleen tumors before it’s too late.


Hemangiomas are non-cancerous skin lesions that look a lot scarier than they are.  Frankly, if I saw one on my dog I’d be nervous.  These vascular lesions can be red or blackish and can also ulcerate.  I’ve looked at different images of hemangioma online and most look like raised, deep red, and remind me (a bit) of how raspberry looks.  Others (see the photo below) looks like red dots.  The image below is a hemangioma on human skin.

Here’s the problem:  Tumors like hemangiomas are not visible to the naked eye. The veterinarian would have reason to believe there’s a tumor on the spleen, but the only way to diagnose it through a splenectomy.  At that point, they can test the tumor. What a relief to find out it’s benign!   Removal of the spleen means you don’t have to worry about cancer ever developing there.  However, please remember that aggressive tumors like hemangiosarcomas can occur on other organs including the heart, liver, and skin.

There’s no Second-Guessing Dog Spleen Tumors

If you see or feel anything on your dog that is out of the ordinary, don’t just shrug it off.  Even your veterinarian can’t “guess” what it is. He/she will have to biopsy the fluid in order to make a determination.  With experience, it’s likely the veterinarian has a pretty good idea what’s happening through a physical examination, but a biopsy will tell the real story.

As I mentioned above, it’s a much different scenario when the tumor is on the spleen or some other organ. You can’t diagnose what you can’t see and, unfortunately, it’s sometimes not until the dog dies that the veterinarian is able to identify the cancerous mass.  In the scheme of things, aggressive dog spleen tumors like hemangiosarcoma have a poor outcome.

If the veterinarian does suspect there is a tumor on the spleen, the spleen will need to be removed. If test results come back benign, you have hope. If the test results show cancer after the spleen is removed, there’s a good chance the cancer has already spread to other organs.

Chemotherapeutic Options

Chemotherapy can be offered after the spleen is removed as a way of trying to catch any remaining cancer cells in the body.  It’s said that dogs handle chemotherapy treatment better than humans and do not lose their fur as a result of it. However, the best case scenario is usually a life of extension of two or three months.

That said, I’ve read a few accounts of owners whose dog lived at up a year after splenectomy. Those as the lucky ones.

Post Surgical Vaccinations

Packerland Veterinary Center in Green Bay, Wisconsin, offers a customized vaccine for dogs with hemangiosarcomas.  They require a big enough sample of the tumor in order to be able to create the appropriate vaccination.  If you’re interested in this option, here are some questions you may want to ask them:

1. Do you have to live in the Green Bay area to access this service?

2. Can I ask my veterinarian to refer my dog?

3. How do you create the vaccine and how does it work?

4. Will it extend my dog’s life and, if so, for how long?

5. Are there side-effects that I should know about?

6. What is the cost?

You can find out more about this new technology by visiting Packerland Veterinary Center . 

PHEW! I’ve given you a lot of information to think about!

Please remember that I’m not a veterinarian and although I research carefully, there’s always the chance that I got something wrong. If you see any errors within this post, please let me know so that I can fix the problem.  Feel free to contact me directly at [email protected]

Thank you so much for taking the time to read my post. Stick around, because there are plenty useful articles here. For example, discover 5 Clinical Signs of Fatty Tumors in Dogs OR 11 Potent Treatment Options for Lick Granulomas.

I hope what you’ve read has been helpful. I want to get to know all of my readers so please feel free to give me a shout. I love hearing from everyone so don’t be shy.