What should you know about mediastinal lymphoma in dogs?

The mediastinum is the central space between the lungs. A lymphoma mass there may press on the airways, lungs, heart, or oesophagus. Dogs can develop faster breathing, coughing, reduced appetite, tiredness, weight loss, or trouble swallowing. Some dogs show fluid around the lungs, which can make breathing more difficult.

A veterinarian may use an examination, blood tests, chest imaging, fluid sampling, and a needle sample or biopsy to identify the lymphoma type. A PET-CT scan is not suitable for every dog, so the veterinary team will choose tests that answer a specific question.

Arrange a prompt veterinary appointment and bring a list of symptoms, appetite and drinking changes, medicines, and any previous results. Keep your dog calm, avoid strenuous activity, and do not give human medicines unless a veterinarian specifically instructs you. Ask whether the chest needs drainage, what tissue confirmation is required, and how treatment choices fit your dog’s comfort and health.

Treatment may include veterinary chemotherapy, and in selected situations radiotherapy or immunotherapy may be discussed. Stem-cell or CAR T-cell approaches are specialist treatments and may not be suitable or available for every animal. Your veterinarian should explain expected burdens, monitoring, and comfort-focused options.

Seek emergency veterinary care if your dog is struggling to breathe, breathing with the mouth open at rest, has blue or grey gums, collapses, cannot swallow water, or becomes suddenly weak. Keep the journey calm and cool, minimize handling, and call ahead. These signs can reflect chest pressure or fluid and need immediate assessment, regardless of the eventual diagnosis.

Where is the mass and is fluid present? What sample will confirm the diagnosis? Which lymphoma subtype is suspected? What treatment aims are realistic for my dog? How will breathing, appetite, pain, and blood tests be monitored? Which changes mean I should return immediately?