Biopsy or FNAC: Which Test for a Lump in a Pet?

A lump in a pet is not always cancer, and the right test depends on what the lump is made of. FNAC uses a thin needle to pick up loose cells for a quick look, while a biopsy takes a piece of tissue, or the whole lump, for a fuller study. Your vet decides which one fits, and a registered veterinarian reads the result with the examination.

Is every lump in a pet a cancer?

No. Lumps in dogs and cats can be fatty lumps, cysts, pockets of pus called abscesses, warts, swollen glands or growths of different kinds. Lumps become more common as pets grow older, which is why older dogs and cats are checked more often.

Nobody can sort a lump into harmless or serious by touch alone. Size, softness and colour are poor guides, because a small lump may matter and a big one may not. Show your vet any new lump, and go sooner if a lump grows, changes colour, opens, bleeds or seems to hurt. Do not squeeze it, cut it or put anything on it.

What is FNAC and what does it show?

FNAC stands for fine needle aspiration cytology, and cytology simply means the study of cells. For FNAC (Fine Needle Aspiration Cytology), your vet passes a thin needle into the lump and draws out a few cells. These are spread on a glass slide, dried, stained with a dye and studied under a microscope by a pathologist, a vet trained to read cells.

It is quick, and it is often done without anaesthetic, although a nervous pet may need to be held gently or sedated at the vet's choice. FNAC can show that a lump is full of pus, fluid, fat or inflamed cells, or that it holds cells that look like a growth.

Its limit is that it shows loose cells, not how they sit together in the tissue. Sometimes the needle gathers too few cells, or mostly blood. Then the vet may repeat the test or move on to a biopsy.

What is a biopsy?

A biopsy removes a piece of tissue, or sometimes the whole lump. For Histopathology / Biopsy, the tissue goes straight into a preservative liquid called formalin and travels to the lab. There it is cut into very thin slices on glass slides and stained. The pathologist can see how the cells are arranged, whether they push into nearby tissue and often what type of growth it is.

This gives a fuller answer than loose cells, and it is the usual way to confirm what a growth really is. The vet generally takes the sample under sedation or anaesthesia.

If your pet has a lump removed by surgery, ask your vet to send it for testing instead of throwing it away. A lump that looked harmless may still tell the pathologist something important.

Formalin is a harsh chemical. Keep the container closed, away from children and pets, and avoid touching it with bare skin.

What about skin smears and fluid tests?

Not every lump is solid. Some are oozing sores, and some hold fluid. A Skin Impression Smear Cytology presses a slide against a moist sore or ulcer to pick up surface cells. It can show bacteria, yeast and inflammatory cells, but it cannot show what lies deep under the skin.

When a swelling, the chest or the belly holds fluid, a Fluid Examination Routine studies the colour, cloudiness and cells in that fluid. This can help the vet understand why the fluid has collected.

How do vets choose between these tests?

Here is a simple way to think about it:

• A quick first look at a lump: FNAC.
• A firm answer for a growth, or an FNAC that was unclear: biopsy.
• An oozing sore or ulcer: skin impression smear.
• A swelling that holds fluid: fluid examination.

Vets often use more than one, starting with the quick test and moving to the fuller one if needed. A biopsy report usually takes longer than a smear, because tissue must be prepared carefully before it can be read.

Please do not search the internet for photos and decide for yourself. Take the report to your vet and let your vet explain what it means for your pet and what to do next.

Read next

A vet who is examining an older pet's lump often looks at the whole animal, and hormone problems can change skin and coat. Thyroid Profile: How T3, T4 and TSH Fit Together explains the thyroid tests for dogs and cats, and Cushing's and Addison's Disease: Cortisol and ACTH Tests covers two hormone conditions seen in dogs.

Testing in Bhopal

If your vet has taken a smear or a tissue sample, call or WhatsApp +91 88175 01118 to arrange it. The lab at C-200, C Sector, Shahpura will collect free from your home anywhere in Bhopal, and it confirms the method, sample needs and reporting time when you book. Samples from other districts can come by courier, bus parcel or through your vet.