Cause and spread
- Cause
- Many causes: benign growths, infection, inflammation and cancer.
- How it spreads
- It depends on the cause.
Signs to watch for
- A new or growing lump in or under the skin
- A sore that does not heal
- Swollen lymph nodes
- A change in the size, colour or shape of an existing lump
Many diseases look alike. Only a laboratory test can tell them apart, so please see a veterinarian for any sick animal.
How it is diagnosed
A fine-needle aspirate is examined for the type of cells, and many skin tumours should be checked this way before surgery, to rule out mast cell tumours. If cells are not enough or the result is unclear, a tissue sample (biopsy) examined by a pathologist gives a fuller answer. Fine-needle samples cannot always tell benign from malignant, for example in mammary tumours.
- Usually the first testFine Needle Aspiration Cytology (FNAC)Cells drawn from a lump with a fine needle.
- Usually the first testCytologyCells from a lump, fluid or swab.
- Confirms the diseaseHistopathology (Biopsy)A pathologist examines the tissue itself.
- Supports the diagnosisImpression Smear CytologyCells pressed onto a slide from a lesion.
Prevention and control
- Have any new lump checked by a veterinarian
- Do not wait: early diagnosis allows better planning for surgery
Where this information comes from
- Overview of Tumors of the Skin and Soft Tissues in Animals · Merck Veterinary Manual
- Cytology · Merck Veterinary Manual
General information for animal owners and veterinarians, last checked October 2026. It does not replace the advice of your veterinarian, who should decide which tests and treatment your animal needs.