Spleen tumours in dogs: symptoms, tests and treatment

Overview

A lump in the spleen is often called a mass because its cell type is not yet known. Not every such finding is cancer. Common benign findings include a haematoma, a collection of blood, and nodular hyperplasia, a local nodular increase in tissue. Together, these account for about 20–41% of all splenic lesions. A benign splenic mass can often be cured by removing the spleen.

Among incidentally discovered splenic masses without abdominal bleeding, 70.5% were benign and 29.5% malignant. In groups of patients with bleeding splenic masses, haemangiosarcoma has accounted for 63.3–70.4%. This distinction matters: the outlook for an incidental finding without signs should not be inferred directly from figures for bleeding tumours. Haemangiosarcoma is the most common malignant cause of a splenic mass in dogs.

Benign spleen tumours also include haemangioma, a benign blood-vessel tumour. Malignant findings include other sarcomas, lymphoma and mast cell tumours alongside haemangiosarcoma. The tumour type in the tissue report therefore guides further care; not every malignant splenic lesion is automatically treated under the same diagnosis.

Causes

Splenic tumours can arise from different tissues because the spleen contains many cell types. Haemangiosarcoma develops from endothelial cells lining blood vessels. It is biologically different from a benign haematoma. The precise cause of tumour formation is unknown. Inherited factors are suspected to contribute.

Haemangiosarcoma can also form in the heart, liver, skin or muscle. Tumours at different locations do not behave identically. Disease confined to the skin can have a better outlook than the same cancer in the spleen. Ultraviolet sunlight is associated with the skin form, but not with haemangiosarcoma of internal organs.

An enlarged spleen can also cause signs by pressing around the stomach. However, spleen enlargement is not always due to a tumour. Splenic torsion, for example, can obstruct normal circulation and enlarge the organ. Abdominal enlargement or nausea therefore does not identify the origin of the change.

Risk factors

Haemangiosarcoma is usually diagnosed in older dogs, often at 8–10 years of age. Large dogs appear more susceptible. Susceptible breeds include German Shepherd Dogs, Golden Retrievers, Labrador Retrievers and Poodles. This list describes susceptibility to haemangiosarcoma rather than determining the nature of every splenic finding in these breeds.

Rarely, a young dog can develop haemangiosarcoma too. Age therefore does not rule it out when investigations find a suspicious lesion. Bleeding raises suspicion of malignancy compared with an incidental finding without signs. Breed, age and signs of bleeding help assess suspicion before the final tissue result.

Typical symptoms

Early haemangiosarcoma may cause no signs or only mild, vague changes. A splenic lesion may be found incidentally during examination or ultrasound. Signs you may notice at home include:

• Lower activity than usual and tiredness.
• Reduced tolerance of exercise.
• Decreased appetite without an obvious reason.
• Weight loss.
• Visible abdominal enlargement.
• Fainting or an episode of weakness.

These signs are not specific to a spleen tumour. Reduced appetite and weight loss, for example, are observations to record before an appointment. Collapse, pale gums and breathing difficulty associated with rupture are much more urgent warning signs. Heart rate can also increase. In the worst case, internal bleeding can cause sudden death.

Complications and consequences

Haemangiosarcoma spreads rapidly to other organs. Common sites include the lungs and abdominal organs such as the liver. Microscopic metastases may already be present at diagnosis but remain invisible on X-rays and ultrasound. Clear images therefore do not mean spread has not occurred.

There is no known cure for splenic haemangiosarcoma. Without chemotherapy, average survival after surgery is about 2 months. Median survival in dogs receiving chemotherapy after surgery is about 4–6 months. Some dogs live for 6–8 months after chemotherapy. Fewer than 10% are alive a year after diagnosis. These figures concern haemangiosarcoma, rather than benign splenic changes.

The outlook after haemangiosarcoma surgery also depends on disease stage. After surgery alone, reported median survival is about 5.5 months for stage I and about 0.9 months for stage III. For stage II ruptured splenic haemangiosarcoma, the median is below 2 months. A general postsurgical estimate of 2–3 months or less is also reported.

Diagnosis at the vet

The vet assesses general condition and the severity of possible bleeding before further investigations. Blood tests assess health and fitness for surgery. Urine testing and blood-clotting tests may also be included. Sampling abdominal fluid can help investigate bleeding. Abdominal ultrasound locates the mass and looks for free fluid or blood.

Chest X-rays and abdominal ultrasound help investigate haemangiosarcoma spread. CT is sometimes needed. Heart ultrasound looks for a possible right atrial tumour. This may be difficult to detect on ordinary X-rays.

A needle sample from a vascular mass often contains abundant blood, limiting cytology interpretation. Microscopic tissue examination, or histopathology, is recommended for a definite diagnosis. Large mass size alone does not reliably distinguish a benign lesion from every cancer.

The pathologist may need samples from the boundary between the mass and healthy spleen. Areas differing in colour and texture are also examined. Sending the whole spleen to the laboratory helps select suitable sites. Otherwise, a small tumour area may be hidden within a large haematoma.

Before surgery, abdominal ultrasound may miss more than 80% of abdominal metastases outside the liver and spleen. Chest X-rays taken with the dog lying on each side improve detection of lung metastases. Test results therefore contribute to the overall assessment even when no visible spread is found.

Treatment

The vet prescribes treatment and medicines. The usual operation is removal of the spleen, or splenectomy. This both treats the problem and provides diagnostic tissue. With a bleeding rupture, surgery must be performed as quickly as possible to prevent further blood loss.

Before surgery, circulation is stabilised with fluid therapy when needed. Severe blood loss may require a transfusion. Significant bleeding may also require plasma and intensive monitoring. Urgency then depends on bleeding and your dog's condition even if the precise tumour type is not yet known.

For a benign mass, surgery alone may be curative. In haemangiosarcoma, chemotherapy often follows surgery to slow spread. Medication may help preserve good quality of life during the remaining time. Chemotherapy may still be considered to slow disease if visible metastases are already present or surgery is not possible. Its effect is then often more limited.

After surgery, your dog usually stays in hospital for 24–48 hours to monitor heart rhythm and blood volume. An electrocardiogram, or ECG, checks for abnormal rhythms. Most postoperative rhythm disturbances settle within 24–48 hours. They may nevertheless need medication. Other possible complications include ongoing bleeding and pancreatitis.

At home, restrict exercise to short lead walks for the first 2 weeks. Protect the long abdominal incision with a collar or recovery shirt if needed. Blood tests and imaging monitor your dog's condition during chemotherapy. Rechecks are tailored to the diagnosis and treatment chosen.

Wound edges should remain together and the wound clean. Marked swelling, a bad smell or continued bleeding is a reason to contact the practice immediately. Avoid swimming and bathing during healing, as moisture can increase bacteria entering the wound. Removable skin sutures are usually taken out at 7–14 days. Some sutures dissolve beneath the skin.

Do not allow wound chewing: your dog can damage it or remove sutures within seconds. If sutures come out, contact the practice as soon as possible.

Prevention

There is no reliable known method of preventing haemangiosarcoma. Its precise cause remains unknown. Sun protection cannot be considered prevention for splenic haemangiosarcoma, as ultraviolet-related risk concerns the skin form. Abdominal ultrasound can look for a tumour in an at-risk dog. This is an early-detection test rather than a way to prevent formation. Special diets have not been shown to prevent haemangiosarcoma. Avoiding toys or other environmental objects does not reduce risk either. Removing a splenic mass, however, reduces the bleeding risk associated with its rupture.

Important for dog owners

Keep the ultrasound report, operation record and pathology result together. Ask whether the diagnosis is still suspected or already confirmed by tissue testing. Put rechecks in your calendar and keep a brief diary of appetite, movement, breathing and episodes of weakness. When discussing options, distinguish recovery from surgery from the outlook for cancer progression. Further care differs for benign findings and haemangiosarcoma.

At discharge, establish whom to call if your dog worsens, including at night. Sudden collapse, pale gums or breathing difficulty require prompt contact. New vomiting after surgery may be associated with pancreatitis, for example. Report it to the vet treating your dog. If cancer is confirmed, also agree how to assess comfort and enjoyment of everyday activities during treatment.

Frequently asked questions

Is a spleen tumour always cancer?

No. A splenic mass can be benign or malignant. Among incidental masses without signs or abdominal bleeding, 70.5% were benign. This proportion does not apply to every dog arriving as an emergency. The final diagnosis is based on microscopic tissue examination.

Does ultrasound reliably show whether a mass is malignant?

Ultrasound helps identify a splenic mass and fluid in the abdomen. However, an imaging-based suspicion does not replace tissue examination or reliably identify every cell type. Small metastases can also remain invisible on both abdominal ultrasound and chest X-rays.

How long does a dog live with haemangiosarcoma?

For splenic haemangiosarcoma, average survival after surgery without chemotherapy is about 2 months. With chemotherapy, the median is about 4–6 months. Median means half the dogs live for less time and half for longer. It is not an individual dog's prognosis.

Can removing the spleen cure a dog?

A benign splenic mass can be cured by surgery. In contrast, there is no known cure for haemangiosarcoma. Even then, surgery may stop bleeding from the mass or reduce rupture risk. Discuss treatment goals before the procedure if circumstances allow.

When can normal exercise resume after surgery?

For the first 2 weeks, exercise is limited to short lead walks. A collar or recovery shirt can protect the wound. The vet treating your dog assesses return to activity according to recovery. Discharge instructions and agreed examinations determine your dog's progression.