Vet Insights: Spleen Cancer in Dogs – How to Recognize and Respond

Spleen Cancer in Dogs: How to Recognize and Respond
In this article, you'll discover everything you need to know about splenic cancer in dogs—what it is, the early warning signs, possible causes, diagnostic methods, treatment options, and more.

What is Spleen Cancer in Dogs?

The spleen, an organ similar in structure to a lymph node but much larger, plays a vital role in the immune system by protecting the body from disease.

Its primary function, however, is as a blood filter, removing old or damaged red blood cells—a role that has earned it the nickname "the red blood cell graveyard."

Spleen cancer occurs when abnormal cells grow and reproduce rapidly, disrupting the spleen's normal functions. This cancer can be malignant, spreading to other organs and tissues, or benign, remaining localized.

Types of Spleen Cancer in Dogs

Spleen tumors are common in older dogs and can be either malignant or benign.

Malignant tumors are aggressive, often spreading to other organs and tissues. While benign tumors don’t spread, they can still pose a serious risk if they rupture, leading to internal bleeding and potentially life-threatening illness.

Spleen tumors can be primary, originating in the spleen, or secondary, resulting from cancer that has spread from another organ. They may also be focal, confined to one area, or diffuse, spreading throughout the spleen.

Primary Spleen Cancer in Dogs

Primary spleen cancer originates in the spleen rather than spreading from another body part. In dogs, the most common types are splenic hemangiosarcoma (malignant) and hemangioma (benign).

Hemangiosarcoma in dogs

Hemangiosarcoma (HAS) is the most common primary spleen cancer in dogs, arising from the endothelial cells that line blood vessels. This cancer is highly aggressive, often causing internal bleeding, and carries a poor prognosis even with treatment.

This primary malignant splenic cancer is most common in middle-aged and older dogs, though isolated cases have also been diagnosed in younger dogs under three years old.

Golden Retrievers, Labrador Retrievers, German Shepherds, and their crossbreed are particularly prone to this type of splenic cancer. An older large-breed dog is usually at risk.

Hemangiosarcoma holds the distinction of being the most aggressive cancer in dogs, with the intra-abdominal organs and the lungs typically bearing the tumor spread.

Splenic rupture may cause your pet to bleed slowly, leading to sudden death.

Unfortunately, hemangiosarcoma is often diagnosed too late because its clinical signs are typically subtle or hidden. When it outgrows the spleen's capacity to contain it, it can rupture, leading to a bleeding splenic tumor.

This is a medical emergency, not only due to the bleeding but also because a ruptured tumor can spread cancer to other body parts.

Hemangioma can develop in any vascularized tissue (or those affecting the blood vessels). However, in addition to the spleen, hemangiosarcoma (HAS) is commonly diagnosed in locations such as the heart, skin, and subcutaneous tissue.

Hemangioma in dogs

Hemangioma is a benign (non-cancerous) tumor arising from the endothelial cells that line blood vessels, similar to hemangiosarcoma (HAS). While hemangiomas are not malignant and do not spread, proper diagnosis and treatment are crucial to prevent complications such as internal bleeding.

This benign disease usually has a favorable prognosis if diagnosed early. However, it is important to remember that guidance from a vet is essential.

Secondary Spleen Cancer in Dogs

Secondary spleen cancer, also known as metastatic spleen cancer, occurs when cancer spreads to the spleen from a primary site elsewhere in the body, such as the skin, liver, or lymph nodes.
Due to its rich blood supply, the spleen is a common site for metastatic cancers. Common malignant tumors of the spleen in most dogs include the following:

• Lymphoma, a malignant cancer caused by uncontrolled lymphocyte growth, often affects lymphoid tissues such as the lymph nodes, thymus, bone marrow, or spleen. While it can also appear in the eyes, skin, or central nervous system (rarely), splenic lymphoma often presents as solitary nodules. It typically has a poor prognosis due to its aggressive nature.
• Leukemia, a rare cancer of the blood and bone marrow, is marked by uncontrolled white blood cell proliferation. It can be acute, progressing rapidly with a poor prognosis, or chronic, which progresses slowly and is manageable long-term. Both types can originate in the spleen or infiltrate it diffusely.
• Mast cell tumors (MCT), originating from immune system white blood cells, are most often found in the skin but can also affect the bone marrow, liver, or spleen. Cutaneous MCT is common in dogs, ranging from mild (good prognosis) to aggressive and metastatic (poor prognosis), with metastases frequently involving the lymphatic system, spleen, kidneys, bone marrow, heart, and lungs.
• Plasma cell tumors (PCT) arise from plasma cells, immune system white blood cells that produce antibodies. Uncontrolled growth leads to cancer, which may be malignant (e.g., multiple myeloma) or benign. PCT can affect the bone marrow, liver, and gastrointestinal tract, with metastases to the kidneys, spleen, and lymph nodes.
• Histiocytic sarcoma, an aggressive cancer arising from dendritic cells, can affect any breed but is more common in Bernese Mountain Dogs and Rottweilers. It typically occurs in the bones, joints, skin, and lungs, but can also, rarely, originate in the spleen.

Less common types of malignant secondary splenic cancers in dogs include melanoma, carcinoma, and leiomyosarcoma. Prognosis varies based on the cancer type and its aggressiveness.

Causes of Spleen Cancer in Dogs

As with most cancers, the causes of canine spleen cancer are not well understood. In humans, hemangiosarcoma may be linked to environmental toxins like arsenic, thorium dioxide, vinyl chloride, and radiation therapy.

In dogs, factors contributing to splenic tumors include:

• Age: Older dogs are more prone.
• Breed: Common in Golden Retrievers, Labrador Retrievers, and
• German Shepherds.
• Size: Large and giant breeds are more affected.
• Sex: Males are at higher risk.
  
• Sex hormones
• Environmental factors, Such as secondhand smoke.

Clinical Signs of Spleen Cancer in Dogs

Indicators of spleen cancer in dogs are often absent or subtle in the early stages. In advanced stages or with internal bleeding, the following signs may appear:

• Lethargy and weakness: The dog may have reduced energy levels and seem unusually tired.
• Decreased appetite and weight loss: The dog may eat less than usual, leading to noticeable and potentially progressive weight loss.
• Abdominal distension: A dog may appear to have a swollen abdomen due to an inflamed spleen or fluid accumulation, possibly blood from a ruptured tumor. Discomfort or pain may cause the dog to avoid touch or adopt unusual positions.
• Pale gums: A sign of anemia, often caused by internal bleeding from a ruptured splenic tumor.
• Shock and collapse: Symptoms like rapid heartbeat, weak pulse, cold extremities, and collapse may indicate internal bleeding.
• Difficulty breathing: Rapid or labored breathing may occur, especially with severe internal bleeding or fluid in the chest cavity.
• Muscle weakness: Tremors and weakness may occur with internal bleeding.

What are the first signs of spleen cancer in dogs? It is often diagnosed incidentally during routine exams or in advanced stages, as early signs are subtle or absent, making definitive diagnosis challenging.

Final Stages of Spleen Cancer in Dogs

The final stages of spleen cancer in dogs, especially in the case of hemangiosarcoma, are often marked by a significant decline in the dog's health and general condition. As the disease progresses, symptoms become more severe, and the dog's quality of life worsens.

Clinical signs in the final stages of spleen cancer in dogs may include severe lethargy, loss of appetite, significant weight loss, severe abdominal distension, and breathing difficulties (especially if the cancer has spread to the lungs or there is internal bleeding).

Symptoms of a Benign Spleen Tumor in Dogs

Benign spleen tumors in dogs may cause no noticeable signs if small or slow-growing, allowing the dog to lead a normal life. However, large or ruptured tumors causing internal bleeding can produce symptoms similar to malignant splenic tumors.

Emergency surgery is required when this happens, or your dog may eventually succumb to an unexpected death.

How is Canine Spleen Cancer Diagnosed?

Diagnosing spleen cancer in dogs involves various methods, including:

• Physical examination: A physical exam includes palpating the abdomen to check for an enlarged or tender spleen, as large tumors can be felt through the abdominal wall. Signs like poor condition, anemia, or abdominal distension may indicate spleen cancer, but a physical exam alone cannot confirm the diagnosis.
• Blood chemistry and Complete Blood Count (CBC): Spleen cancer does not directly appear in blood work, but blood tests help assess a dog’s overall health and organ function. Elevated liver enzymes or other abnormalities may indicate metastasis to organs like the liver. Internal bleeding may cause anemia on a CBC, along with abnormal platelet and white blood cell counts.
• Coagulation tests (prothrombin and partial thromboplastin time): Assess the risk of internal bleeding by measuring blood clotting time.
• Abdominal ultrasound (AUS): Considered a valuable tool for detecting splenic masses, ascites, or internal bleeding. It can also guide tumor sampling for diagnosis.
• X-rays and chest radiographs: Necessary to evaluate the spleen in relation to other abdominal organs, but also to see if there are metastases in the thoracic or abdominal cavity.
• Computed Tomography (CT) or Magnetic Resonance Imaging (MRI): These tests are recommended when it is desired to accurately determine the extent of the tumor or metastases.
• Abdominal fluid analysis and cytology: When a splenic tumor ruptures, it causes internal bleeding. The blood collects in the abdomen. Your vet may take a sample of the abdominal fluid and examine it under a microscope to assess the cell population (whether or not there are tumor cells).
• Biopsy: Involves sending pieces of the splenic tumors to a histopathologist for examination and confirmation of the presence of cancer and its type. A complete spleen biopsy can be performed surgically, usually during a splenectomy (surgical removal of the spleen).

Treatment For Spleen Cancer In Dogs

Treatment for splenic tumors in dogs depends on the tumor's nature (benign or malignant), disease stage, and the dog's health.

Surgery is often recommended for both types, as even benign tumors can rupture and pose a life-threatening risk, such as in the case of a ruptured splenic tumor. You must consult a veterinary oncologist for guidance.

Having the whole spleen removed is not uncommon.

Since the spleen is not vital, veterinarians remove it entirely rather than just the tumor. Dogs, like humans, can live without a spleen without major complications.

However, surgery may not be recommended if the dog is unfit for anesthesia due to conditions like heart disease or if the cancer is at an advanced stage and has spread.

For benign tumors with no metastasis or complications, the prognosis is typically good after surgery. However, with hemangiosarcoma and other malignant tumors, metastases are common, and outcomes are often less favorable despite spleen removal.

Adjuvant chemotherapy, often with drugs like doxorubicin, is commonly used after splenectomy to prevent or treat metastases, especially in cases of hemangiosarcoma.

Depending on the case, vets can also recommend blood transfusions, steroid medication, and various supplements.

Life Expectancy of Dogs with Spleen Cancer

Survival time for dogs with spleen cancer varies based on cancer type, stage, treatment, health, and age. Untreated dogs with malignant cancer may live weeks to months. Treated dogs can survive months to a year.

If the tumor ruptures, survival ranges from days to months, depending on blood loss. Ruptured splenic tumors may potentially lead to life-threatening blood loss in some cases.

A dog dying of hemangiosarcoma may suffer from metastasis, a ruptured tumor causing internal abdominal bleeding, or a large tumor pressing on organs. Symptoms include difficulty breathing, pale gums, severe lethargy, weight loss, muscle tremors, and abdominal tenderness. Immediate veterinary care is essential.

Should you euthanize a dog with hemangiosarcoma? If treatment is ineffective, the cancer has spread, surgery isn’t an option, and your dog is suffering, humane euthanasia may prevent unnecessary pain.

Can Spleen Cancer in Dogs Be Treated Naturally?

Natural treatments can support your dog’s recovery and immune system, but cannot cure cancer. They enhance well-being and offer a gentler alternative to conventional treatments.

PIPTOPET is designed to support your dog during splenic tumors and cancers.

PIPTOPET is a natural product containing birch polypore (Fomitopsis betulina), a medicinal mushroom with antiviral, antibacterial, antitumoral, anti-inflammatory, immune-boosting, and antioxidant properties. Known for its benefits for centuries, it may help dogs fight spleen cancer and recover, as supported by studies on animals.

PIPTOPET is an excellent product for dogs with spleen cancer, supporting the immune system and natural healing. To enhance its effects, consider adding the following homeopathic remedies to your dog's treatment:

• TONICPET #4: Supports your dog’s overall vitality by assisting the body’s natural processes involved in oxygen transport and immune function.
• TONICPET #5: Helps maintain healthy blood flow and supports your dog’s natural circulation, contributing to overall wellness.
• TONICPET #7: Promotes healthy oxygen distribution throughout the body, helping to support energy levels and the body’s natural defenses.
• TONICPET #10: Supports the body’s natural pH balance, helping to maintain a healthy internal environment that contributes to your dog’s general wellbeing.

The spleen, part of the lymphatic and immune systems, supports circulation and natural defenses. These remedies enhance both, helping your dog fight cancer more effectively.

CBD oil helps keep tumor tissue in check.

CBD oil (cannabidiol) is another product that can help your dog fight spleen cancer because it can cause the programmed death of cancer cells (apoptosis) and reduce cell viability.

Additionally, if your dog is cancer-free, these products can help boost and maintain splenic health.

Can You Prevent Spleen Cancer in Dogs?

Here's the thing: spleen cancer cannot be prevented, but annual vet checkups can help catch it early for timely treatment. Many dogs tend to have splenic masses that go undetected because of this.

Monitor your pet's behavior, provide a balanced diet, and avoid harmful chemicals by using pet-safe cleaning products. It is also helpful to regularly consult a veterinarian or a pet homeopathy expert for some tips and tricks in keeping your dog's health ideal.

About the author

Dr. Iuliana Mihai, DVM, MSc, PhD

Iuliana Mihai, DVM, MSc, PhD, is a Bucharest-based veterinary expert specializing in internal medicine and oncology.

Her work has been published in reputable publications such as Veterinary Medicine Journal, Catster.com, Dogster.com, Hepper.com, Meowiz.com, Springnaturals.com, Petkeen.com, and Wilderharrier.com.

She is a malpractice and negligence veterinary consultant and a graduate of The University of Agronomic Sciences and Veterinary Medicine and The Romanian Academy.

Read the complete profile of Dr. Iuliana Mihai, DVM, MSc, PhD (Veterinarian) here.