Lumps and Bumps on Pets: When Should You Be Concerned?

Discovering a new lump on a dog or cat can be alarming. Some masses are harmless fatty growths, cysts or warts, while others may be inflammatory lesions or tumours that require treatment.

Unfortunately, it is not usually possible to determine whether a lump is benign or malignant by appearance or touch alone. A soft, slow-growing mass may still need testing, while a firm or rapidly changing lump does not automatically mean cancer.

At Lonsdale Place Veterinary Clinic, we recommend documenting new masses and having them assessed rather than relying on guesswork.

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What Counts as a Lump or Mass?

A mass is any abnormal swelling, thickening or growth found on or beneath the skin.

It may feel:

• Soft or firm

• Smooth or irregular

• Fixed in place or movable

• Painful or painless

• Fluid-filled or solid

• Superficial or deep beneath the skin

Some masses remain unchanged for years. Others enlarge, become inflamed or change very quickly.

Lumps may occur anywhere, including:

• The chest or abdomen

• The legs and paws

• The head or neck

• Beneath the tail

• Around the mouth

• Along the mammary glands

• Beneath the skin

• Inside the ear

• Between the toes

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Are All Lumps Cancerous?

No. Many skin and subcutaneous masses are benign. Common non-cancerous possibilities include fatty masses, cysts, warts, blocked glands and areas of inflammation.

However, cancerous masses can resemble benign growths. Some mast cell tumours, for example, may look like a wart, insect bite or allergic swelling and can fluctuate in size.

This is why appearance alone is unreliable.

The safest principle is simple: a lump should be sampled rather than watched indefinitely when its identity is unknown.

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Common Types of Lumps

Lipomas

Lipomas are benign fatty masses commonly found beneath the skin of middle-aged and older dogs.

They are often:

• Soft

• Movable

• Slow-growing

• Painless

Even when a mass feels typical of a lipoma, sampling is generally recommended to confirm that it contains fat cells. Other tumours can occur in the same locations and may feel similar.

Some benign fatty masses become large enough to interfere with walking, lying down or normal limb movement. In those cases, removal may be discussed despite the mass being non-cancerous.

Cysts

Cysts are sacs that may contain fluid, keratin or other material.

They may appear as:

• Smooth, rounded bumps

• Firm nodules

• Growths with a visible pore

• Lumps that periodically rupture or drain

Do not squeeze a suspected cyst. Rupturing it may cause pain, inflammation or infection, and the lump may refill if its lining remains.

Warts and Papillomas

Papillomas are wart-like growths that are particularly common in dogs. Some are associated with viruses and may resolve as the immune system responds, especially in younger dogs. Others persist or become irritated.

A wart-like appearance does not guarantee that a mass is benign. Other tumours can have a similar surface.

Abscesses

An abscess is a pocket of infection beneath the skin. It may develop after a bite wound, puncture or foreign object.

Possible signs include:

• Sudden swelling

• Heat

• Pain

• Redness

• Pus or discharge

• Fever

• Reduced appetite

• Low energy

Abscesses can enlarge quickly and may rupture. They require veterinary assessment and often need drainage, cleaning, pain relief and sometimes antibiotics.

Insect Bites and Allergic Swellings

Bites or stings may cause a temporary raised area. Allergic reactions can also produce multiple small bumps called hives.

Seek urgent care if swelling is accompanied by:

• Facial swelling

• Vomiting

• Weakness

• Collapse

• Difficulty breathing

• Pale gums

• Rapidly worsening symptoms

Malignant Tumours

Cancerous masses vary widely. They may be soft or hard, fast- or slow-growing, painful or painless.

Features that increase concern include:

• Rapid growth

• Ulceration

• Bleeding

• Irregular shape

• Firm attachment to deeper tissue

• Recurring after removal

• Changing size

• New pain

• Nearby lymph-node enlargement

However, the absence of these features does not confirm that a mass is harmless.

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What Is a Fine-Needle Aspiration?

A fine-needle aspiration, or FNA, is a commonly used test for lumps and bumps.

A small needle is inserted into the mass to collect cells. The cells are placed on microscope slides and evaluated either within the clinic or by a veterinary pathologist.

FNA is widely used to sample external masses and can also be used for lymph nodes, internal organs and abnormal fluid collections.

Many pets tolerate the procedure while awake because the needle is similar in size to one used for an injection. Sedation may be recommended when:

• The mass is painful

• The pet is very anxious

• The location is sensitive

• The pet cannot remain still safely

• Ultrasound guidance is required

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What Can an FNA Tell Us?

Cytology may identify:

• Fat cells consistent with a lipoma

• Inflammatory cells

• Bacteria or infection

• Cyst contents

• Mast cells

• Lymphoma

• Other tumour-cell populations

Sometimes the sample is not diagnostic because the mass does not release enough cells or because tissue architecture is needed to identify it accurately.

When cytology is inconclusive, a biopsy may be recommended.

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What Is a Biopsy?

A biopsy collects a piece—or sometimes all—of the mass for histopathology.

A pathologist evaluates how the cells are arranged within the tissue. This can provide information that a needle sample cannot, including:

• The precise tumour type

• Whether it is benign or malignant

• How aggressive it appears

• Whether a removed mass has clean surgical margins

• Whether additional surgery or treatment may be needed

Lumps are often impossible to diagnose by appearance alone, while microscopic evaluation of cells or tissue can provide a classification and diagnosis.

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Why Sample Before Removing a Mass?

Owners sometimes ask why a veterinarian would sample a lump if it is going to be removed anyway.

Knowing the likely type of mass before surgery can help the veterinarian plan:

• How wide the surgical margins should be

• Whether imaging is needed first

• Whether nearby lymph nodes should be sampled

• Whether referral is appropriate

• Whether removal is urgent

• Whether another treatment should be performed first

A benign mass may be removed with relatively narrow margins. Certain malignant tumours require a wider removal that includes apparently normal surrounding tissue.

AAHA senior-care guidance recommends fine-needle aspiration of masses before surgery so appropriate margins can be planned.

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Should Every Lump Be Removed?

Not necessarily.

The decision depends on:

• The diagnosis

• Size and location

• Rate of growth

• Whether it causes pain

• Whether it interferes with movement

• The pet’s age and overall health

• The likelihood of malignancy

• Whether the mass is ulcerated or infected

• Surgical and anesthetic considerations

A confirmed benign mass that remains small and causes no discomfort may sometimes be monitored. A mass on a paw, eyelid or joint may require removal sooner because even a small amount of growth can interfere with function.

Monitoring should be an active plan, not simply forgetting that the lump exists.

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How to Monitor a Lump at Home

Create a record containing:

• The date it was first noticed

• Its exact location

• Approximate length and width

• A clear photograph

• Whether it is soft or firm

• Whether it moves beneath the skin

• Any redness, bleeding or discomfort

Place a ruler or coin beside the mass when photographing it to show scale.

Recheck it regularly and note any changes. A body map can be particularly useful for pets with multiple masses.

Do not repeatedly squeeze or manipulate the lump. This may irritate certain types of masses and make changes more difficult to interpret.

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Changes That Require Prompt Assessment

Arrange an appointment when a lump:

• Is newly discovered

• Is increasing in size

• Changes colour or texture

• Becomes red or swollen

• Bleeds or develops an open surface

• Produces discharge

• Becomes painful

• Suddenly changes size

• Interferes with walking, eating or toileting

• Returns after previous removal

• Is located inside the mouth

• Is associated with weight loss or reduced appetite

Any mass can be evaluated, regardless of how long it has been present. Owners should not avoid mentioning an older lump because they are worried it has been there “too long.”

Special Considerations for Cats

Cats can develop benign and malignant masses just as dogs can. Any persistent lump in a cat should be assessed.

For a mass arising near a previous injection or vaccination site, veterinary guidelines use the 3-2-1 rule as a reason to pursue biopsy:

• The mass remains present for three months.

• It is larger than two centimetres.

• It is increasing in size one month after the injection.

A mass meeting any of these criteria warrants further investigation.

This does not mean every post-injection swelling is cancerous. Small, temporary swellings can occur, but persistent or enlarging masses should not be ignored.

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Do Not Wait for a Lump to Become Painful

Many tumours do not hurt during their early stages. A pet may continue eating, playing and behaving normally despite having a significant mass.

Waiting for pain or illness before arranging an examination can allow a tumour to become larger and more difficult to remove.

Earlier assessment may provide:

• More treatment options

• A smaller surgical procedure

• Better surgical margins

• Faster relief from discomfort

• More useful information for planning

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What to Expect at the Appointment

The veterinary team may:

1. Examine and measure the mass.

2. Check the rest of the body for additional lumps.

3. Examine nearby lymph nodes.

4. Perform a fine-needle aspiration.

5. Recommend cytology or histopathology.

6. Discuss bloodwork or diagnostic imaging.

7. Develop a monitoring or treatment plan.

Depending on the suspected diagnosis, chest X-rays, abdominal ultrasound or lymph-node sampling may be recommended before surgery.

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Have New Lumps Checked Early

Most newly discovered lumps are not emergencies, but they should not be diagnosed by appearance or touch alone.

Contact Lonsdale Place Veterinary Clinic when you find a new mass or notice a change in an existing one. Sampling is often quick and minimally invasive, and the information gained can help distinguish a harmless growth from one requiring timely treatment.

Finding a lump can be worrying, but early evaluation replaces uncertainty with a clear and informed plan.