Lumps, bumps and skin lesions are one of the most common reasons pets are brought to the vet — and for good reason. A large number of tumours in both dogs and cats are associated with the skin. While many of these growths may be harmless, others can be serious or even life-threatening if left untreated.

The most important message for pet owners is simple: early detection gives your pet the best possible chance of successful treatment. Any new, changing, or unusual lump should be examined by your veterinarian.

Why You Can’t Diagnose a Lump by Looking or Feeling It

Unfortunately, neither vets nor doctors can reliably determine what a lump is simply by looking at it or feeling it. In some cases, the cause may be obvious — for example, an abscess resulting from a bite wound. However, in many situations, further investigation is needed to understand what’s happening beneath the surface.

This is why diagnostic testing plays such an important role in deciding the next steps.

Fine Needle Aspirates: A Simple but Powerful Test

One of the most common first diagnostic tools we use is a fine needle aspirate (FNA). This involves taking a very small sample of cells from the lump using a fine needle, placing the material on a slide, staining it, and examining it under a microscope.

This process is called a cytological examination, which allows us to analyse the cells present in the lump. While it doesn’t always provide a definitive diagnosis, an adequate sample often helps us determine whether a lump is:

• Benign (non-cancerous)
• Malignant (cancerous)
• Inflammatory
• Infectious
• Or related to another disease process

This information is crucial in guiding further decisions.

Deciding on Surgery and Treatment

Based on the results of the cytology, we can decide:

• Whether the lump should be removed
• How urgently it needs to be addressed
• How much surrounding tissue may need to be removed
• Whether additional tests or treatments are required

If a lump is suspected to be malignant — or if we’re uncertain about its nature — we often recommend surgical removal or a biopsy.

Histology: Getting a Definitive Diagnosis

When a lump or tissue sample is sent to a laboratory, it undergoes histological examination. A specialist pathologist examines thin, stained sections of the tissue to make an exact diagnosis.

Histology can often tell us:

• The precise type of tumour
• Whether the growth is benign or malignant
• How aggressive it may be
• Whether the entire lump was likely removed during surgery

Sometimes only a portion of the lump (a biopsy) is sent for analysis first. This allows us to plan the most effective treatment approach while minimising unnecessary surgery or complications.

Checking for Spread (Staging)

If a tumour is confirmed to be malignant, further tests may be recommended to assess whether it has spread. These may include:

• Chest X-rays
• Abdominal ultrasound
• Testing or sampling nearby lymph nodes

This process, known as staging, helps us understand the full picture and decide what additional treatment — if any — is required.

The Bottom Line

Lumps and bumps should never be ignored. Even growths that seem small, painless, or unchanged can hide serious disease.

Early detection and early intervention give your pet the best chance of a positive outcome. If you notice any new lump, bump, or skin lesion — or if an existing one changes in size, shape, or appearance — bring your pet in for an examination as soon as possible.

If you’re ever unsure, it’s always better to check.