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There's a lump on the back of my dog’s neck. What should I do?

Lumps in dogs can occur for multiple reasons and there are a vast array of different types ranging from benign and harmless to highly malignant and potentially life threatening. A lump on the back of your dog’s neck can be any one of the lumps commonly seen in dogs, but it is worth also taking into consideration vaccination. If your dog has been vaccinated within the last three weeks it is fairly normal to be able to feel a small lump usually around 2cm in the scruff of your dog’s neck where the injection was given. Our vet explains about the possible causes of a lump on the back of your dog’s neck.

This article was written by a FirstVet vet


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A lump on the neck can persist for a couple of weeks after a routine vaccination, however, this is rare. The lump may also be accompanied by other signs such as tenderness in the area, general lethargy and being off colour. If the lump seems to be growing, or your dog has not been recently vaccinated, it is important to book an appointment with your vet to perform a full examination and potentially sample the lump.

Common causes of lumps in dogs

  • Vaccination site reaction

  • Skin tag

  • Skin reaction to an insect bite

  • Lipoma (fatty lump)

  • Sebaceous cyst

  • Abscess

  • Hives

  • Histiocytoma

  • Wart (Papilloma)

  • Hygroma (a soft swelling filled with fluid usually over a joint)

  • Haematoma

  • Mast Cell Tumour

  • Melanoma

  • Soft Tissue Sarcoma

  • Squamous Cell Carcinoma

Diagnosis of your dog’s lump

The lump is often sampled using a small needle to take some cells. These cells are analysed under the microscope to identify their origin and any indications of malignancy. Sometimes it is not possible to achieve a definitive diagnosis in this way, in which case your vet will recommend removing a larger biopsy sample, or the whole lump, for analysis. This is usually performed under general anaesthesia. Surgery may be straight forward or complex depending upon size, location, infiltration into surrounding tissue and the type of mass present.

If analysis of the lump indicates a malignant tumour then sometimes further treatment such as chemotherapy or radiotherapy is required.

Remember! Not all lumps in dogs are cancerous but having them examined by your vet and tested is the safest way to monitor any lumps and bumps your dog might have.

When to see your vet?

  • The lump has persisted beyond 3 weeks

  • The lump has rapidly changed in size, shape, colour or changes in the overlying skin

  • The lump is accompanied by any of the general signs above

Still worried?

Book a video appointment to have a chat with one of our vets.

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