Splenic Masses in Dogs

Written by Shula Berg BVSc CertAVP(GSAS) GPAdvCert(SASTS) MRCVS
Clinically reviewed by Elizabeth McLennan-Green BVM&S CertAVP(SAM) MRCVS

Table of Contents

- Overview
- Symptoms
- Diagnosis
- Treatment
- Outlook

What are Splenic Masses?

The spleen is a very vascular organ that sits in the middle of the abdomen. Enlargement of the spleen is sometimes found on examination, during palpation of the abdomen, or during an ultrasound scan. Enlargement of the spleen can be diffuse, or due to a mass within or on the organ. There are many causes of splenic enlargement, both cancerous and non-cancerous, and it is often very difficult to determine between them. 

More than half of all splenic masses are caused by malignant (aggressive) tumours, with the remainder caused by benign tumours, or non-cancerous changes. The spleen is a common site for tumours to spread (metastasise) to, so many dogs with cancer in the spleen will also have cancer elsewhere in the body. 

What are the symptoms of Splenic Masses? 

Many splenic masses have no outward symptoms, and it is not uncommon for them to be found without prior warning. If the mass is large, it can put pressure on the stomach (causing vomiting or reduced appetite), or cause visible abdominal distension. As the spleen is very vascular, some large splenic masses will cause anaemia, seen as lethargy or reduced exercise tolerance. 

Some splenic tumours are fragile, and can spontaneously bleed in to the abdomen. This may cause episodes of weakness or collapse, and contribute to anaemia. Occasionally, the tumour can rupture causing massive blood-loss. Affected dogs often collapse and will need emergency treatment. Any splenic mass has potential to bleed, but this is generally seen more often with aggressive tumour types. 

Which tests are used to diagnose Splenic Masses? 

The presence of a splenic mass is typically diagnosed (or confirmed) using ultrasound, which allows a non-invasive assessment. A blood sample will often be recommended, if not already performed, to check for anaemia and other changes. 

Since a considerable number of splenic tumours will spread elsewhere in the body, it is often recommended to examine other areas prior to treatment. This often involves chest x-rays, ultrasound of the other abdominal organs, and sometimes ultrasound of the heart. Your vet will advise you on the most appropriate steps. 

The only reliable way to determine what type a splenic mass is, is with a solid tissue biopsy. This allows the lab to examine the individual cells and how they are structured in relation to each other. Needle samples don’t usually provide a diagnosis, and can instigate bleeding. Due to the vascular nature of the spleen, a surgical biopsy will cause a very high risk of haemorrhage. Instead, removal of the spleen (splenectomy) is performed for both diagnosis and treatment. Adult dogs do not need a spleen and removal of this organ has no long term impact. 

How are Splenic Masses treated?

Surgery is the treatment of choice for splenic masses and, as discussed above, is usually performed without a definitive diagnosis. For masses that are not bleeding, a splenectomy is a planned procedure and is usually routine, with few specific risks. If the mass has ruptured, a splenectomy may need to be carried out as an emergency surgery. This is more challenging as dogs are often already anaemic and have low blood pressure due to blood loss, however these will be addressed prior to surgery. A splenectomy may be performed at your normal practice, however if additional care is anticipated, referral to a practice with overnight care facilities may be advised. 

After a splenectomy, it usually takes a couple of weeks to receive results from the external lab, which tell us what the splenic mass was. If this is a non-cancerous change, or a benign tumour, it is likely no further treatment will be needed. If the mass is a malignant cancer, most likely the splenectomy will not have been curative. Additional treatment may be recommended and staging may be advised, if not performed already. 

The most common malignant cancer affecting the spleen is called haemangiosarcoma. This is a very aggressive tumour, and commonly spreads to the liver and heart. Chemotherapy may be considered, however it is important to note that in pets, the aim of chemotherapy is generally to improve quantity of life whilst maintaining a good quality of life. To achieve this, lower doses are used compared to human chemotherapy. The aim is not to cure, but to palliate. Your vet will explain the options for treatment once you have a definitive diagnosis. 

What is the outlook for dogs with Splenic Masses? 

The prognosis for dogs with splenic tumours is variable, depending on the tumour type, and the presence or absence of metastasis at the time of diagnosis.   

In cases with malignant tumours, prognosis is very poor. Depending on tumour type, survival times vary from 3 weeks to 3 months due to the degree of metastases present. Haemangiosarcoma treated with splenectomy followed by chemotherapy has an average survival time of 6-7 months, with 20% of dogs surviving to 1 year post diagnosis. Although in these cases a splenectomy is not curative, it is considered palliative and will extend their lifespan. Sadly, rupture of the spleen is an emergency, and requires immediate surgery or euthanasia. Although a splenectomy will not resolve the cancer, it can allow time to come to terms with the diagnosis and allow you to say goodbye when quality of life becomes poor. 

Splenic masses found unexpectedly, with no evidence of bleeding and no identifiable metastases have a good chance of being benign. In these cases, a splenectomy is advisable for definitive diagnosis and, hopefully, cure. 


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Page last reviewed: 16th January 2024
Next review due: 16th January 2026