
Skin Lumps on Dogs: Types and What They Mean
My dog has a lump, what is it?
Lumps on dogs can have various causes. While most dog skin growths are non-cancerous, it's crucial to have any new lump checked by your vet to rule out serious conditions.
Written by Dr. Mariella Roberts, Veterinary Surgeon, Animal Trust Vets CIC | Published August 2025 | Review date August 2027 | This advice is for UK pets only and is not a replacement for seeing a vet


Types of skin lumps on dogs: lumps vs. tumours
Benign lumps:
Lipomas are soft, fatty tumours that are typically harmless and slow growing.
Cysts fluid-filled sacs under the skin, which can vary in size and appearance.
Skin tags small, fleshy growths that are often found on older dogs.
Sebaceous cysts blocked oil glands that can appear like pimples.
Histiocytomas small, red, button-like growths that are more common in younger dogs.
Papillomas (warts) small, raised growths that are often found on the head and face, caused by a virus.
Potentially malignant lumps:
Mast cell tumours common skin tumours in certain breeds, which can vary in appearance and aggressiveness.
Melanomas can occur in the skin and are sometimes malignant.
Squamous cell carcinomas raised, wart-like patches or lumps, potentially linked to sun exposure.
Basal cell carcinomas flattened or raised growths that can appear anywhere on the body.
Other lumps
Abscesses painful, pus-filled lumps caused by infection or injury.
Calluses thickened areas of skin, particularly on elbows and other joints.
Injection site reactions swelling or lumps can occur at injection sites (vaccinations), which usually resolve on their own.
What are the next steps/will my vets do next?
Physical Examination and History
Taking a history and thorough physical exam is the first steps of the investigation. During the physical exam, your vet may check for lumps elsewhere on the body to see if there are any signs of spread.
Cytology
Fine-Needle Aspirate (FNA)
A small needle is inserted into the lump to collect cells for microscopic examination
It is a procedure used for an initial assessment of lumps, particularly used for skin lumps
The procedure is no invasive
It is less costly than a biopsy
Results can come back inconclusive
Biopsy
A large sample of tissue is surgically removed from the lump
It requires general anaesthetic or sedation
More expensive than FNA, a biopsy provides a more detailed tissue analysis (histopathology) which is often necessary for definitive diagnosis including determining if a tumour is benign or malignant
It is used when FNA are inconclusive or more accurate diagnosis
There are risks associated with any surgical procedure, including bleeding, infection, and pain