Understanding Lumps and Bumps in Dogs and Cats: Causes, Symptoms and Treatment

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As pet parents, finding a lump on your dog, puppy, cat or kitten, can be alarming. While some are harmless and rarely a cause for concern, other lumps may be indicative of an underlying health problem that should be addressed immediately. This comprehensive guide will go through the many types of bumps that occur in dogs and cats, diagnosis, treatment options and when and how pet insurance can help. This guide will help both new and seasoned pet parents alike in understanding what that lump might mean.

What Exactly Are Lumps and Why Do They Appear?

Lumps under our policy refers to: the protuberance or localised area of swelling or unusual growth that can occur anywhere on or in the body including tumours, warts, cysts, growths, mucoceles, haematomas and abscesses.

Lumps can vary in their size, texture and location, and their causes can range from harmless fat deposits to cancerous tumours. Alongside this, some lumps can develop slowly over time or suddenly appear.

Lumps in both dogs and cats can occur due to:

  • Ageing: Older pets are more prone to developing lipomas1.
  • Infections: Bacterial, viral, or fungal infections can cause localised swelling and/or abscesses1.
  • Inflammation: Trauma or irritation can lead to the development of lumps such as haematomas5.
  • Allergic reactions: Raised or flattened, irritable lumps from allergens occurring in the environment, food or insect bites6.
  • Parasites: Bites from parasites such as fleas or ticks can cause a reaction leading to the development of a lump6.
  • Genetic predisposition: Some breeds are genetically prone to develop certain lumps such as mast cell tumours in Boxers or lipomas in Labradors
  • Cancer: Tumours, both benign and malignant, can cause lumps1,3.

Common Types of Lumps Pet Owners Worry About

Before exploring specific lump types, it may be helpful to address some of the most searched lumps looked up by fellow pet parents:

  • Soft, squishy lump just under the skin: Usually just fat lumps, also known as lipomas, these are normally benign and harmless but should still be checked
  • Small, raised bump of the skin: This could be a wart, insect bite, or even a tumour
  • Large, fluid-filled lump: May be a cyst or abscess, these can vary in severity
  • Hard, immoveable lumps: These lumps may be more concerning and should be checked by a veterinarian, as they may be attached to underlying structures and require further diagnostic tests
  • Rapidly growing lump: These warrant immediate veterinary attention as it may be cancerous

Being able to identify and describe the lump can help communicate to your vet and aid in the diagnostic direction that is taken.

The Difference Between Benign and Malignant Lumps

Furthermore, understanding whether a lump is benign or malignant is crucial in determining the potential risk it poses to your pet’s health.

  • Benign Lumps: These are non-cancerous growths that do not spread to other parts of the body. They are generally slow-growing and well-defined. While most benign lumps are harmless, some can grow large enough to cause discomfort or interfere with your pet’s mobility.
  • Malignant Lumps: These are cancerous growths that have the potential to invade surrounding tissues and spread (metastasise) to any other parts of the body, such as vital organs. Malignant lumps often require urgent treatment to prevent further health complications.

The distinction between benign and malignant lumps can only be determined through proper veterinary evaluation using a combination of diagnostic tools such as fine needle aspiration, biopsy, or imaging modalities. Early detection and diagnosis play a vital role in successful treatment outcomes.

Importance for Pet Owners

Understanding and identifying lumps is crucial for pet owners as early detection and intervention can significantly improve outcomes for those lumps that may be more aggressive. Recognising lumps allows pet owners to seek prompt veterinary care and treatments which may include medication, surgery and/or chemotherapy. Also, certain breeds of dogs and cats are predisposed to developing certain lumps and their associated diseases, being able to recognise this and monitor signs early on allows for prompt veterinary care that can change the course of treatment your veterinarian chooses.

Specific Types of Lumps

The following sections cover some of the most common types of lumps that can be found in dogs and cats. Please note that this is not an exhaustive list, but it does highlight the lumps that pet owners are most likely to encounter and worry about. For a more comprehensive understanding or if you suspect a lump that isn’t listed here, always consult your veterinarian and other reliable pet health resources to ensure your pet receives the best care possible.

 

Dogs
TumourDescriptionRisksTreatment
Benign
LipomasSoft, squishy, and moveable lumps just under the skin, fat deposits1.Usually remain benign, however large lipomas can impede mobility and cause discomfort1.No treatment is usually required1. However, if they grow significantly, surgical removal may be necessary1.
FibromasUsually isolated, hairless lumps found on the head and legs1. Can feel firm/rubbery or soft/squishy1.
Are growths of fibrous tissue such as muscle, blood vessels, fat1.
Usually remain benign1.Only requires surgical removal if it grows larger or changes appearance1.
Sebaceous CystsSmall, fluid-filled sacs formed from clogged hair follicles1.Can rupture and become infected1.May drain naturally or require surgical removal if it becomes problematic1.
Warts & Skin TagsOften found in older dogs, can be single or multiple1.Usually harmless but can become irritated1.Rarely requires removal unless obvious signs of infection1.
HaematomasBlood-filled swellings caused by trauma, often seen on the ears5.Painful, but non-threatening5.Draining or surgical correction. May be followed with an antibiotic course if infected5.
MelanomasUsually found on the head and forelimbs, can either be flattened or raised, isolated or multiple darker lumps1.
Common in breeds such as miniature and standard Schnauzers, Doberman Pinschers and Golden Retrievers1.
Usually benign, there is a malignant form however it is uncommon (these would appear as raised, ulcerated lumps)1.Surgical removal1.
Malignant
Mast Cell TumoursMost common skin tumour in dogs, can occur anywhere, can look like a generic lump or progress to ulcerated masses.
Can look like a lipoma1.
Can begin with rash-like signs and progress to vomiting, diarrhoea (high-grade tumours)
If spreads to internal organs, can be fatal1.
Surgical removal and radiation or chemotherapy, based on degree1.
Soft Tissue SarcomasLumps are often found on paws, mouth, or skin, but can occur anywhere with connective/’soft tissues’ such as muscles, neural tissues, fibrous tissues1.
Can appear as isolated or multiple, firm, deep, and fleshy-feeling lumps. Often requires diagnostic tools to determine if it is malignant1.
If spreads to internal organs, particularly the lungs, it can be fatal1.
High rate of recurrence: Even if one lump is removed, there is a highly likely chance that another will occur1.
Surgical removal and radiation, or chemotherapy1.
Squamous Cell Carcinomas (SCC)Most frequently diagnosed skin carcinoma in dogs1.
Two forms:
  1. Skin: Firm, raised, often ulcerated that appear on the head, lower legs, abdomen, and rear1.
  2. Subungual: Originate from under the nail/claw. Frequently associated with dark-haired breeds1.

Are often solitary, however multiple can develop, especially in areas with increased sun exposure1.

The lumps due to the skin form of SCC are sometimes cause by sun exposure, especially in white-skinned, shorthaired breeds1. Before the malignant tumour develops, they will first have solar keratosis1; Solar keratosis is distinguished by thickened and discoloured skin and should be checked by a veterinarian1.

Can often return around 20 weeks post-surgical removal1.

Surgical removal, including amputation of an involved toe or ear1. Combined with radiation treatment or chemotherapy1.

Prevention: reduce exposure to excessive sunlight1.

Cutaneous/ Subcutaneous HaemangiosarcomaCan appear as a red or purple lump or nodule7, bruising or bleeding around the mass. Other symptoms can include lethargy, lameness, loss of appetite or weakness7.When cutaneous haemangiosarcoma is caught early, these dogs typically do well7. However, there are other forms of haemangiosarcoma (subcutaneous, splenic and cardiac) that are much more aggressive and carry a less promising prognosis7.Surgical removal. Other medications may also be administered such as anti-bleeding medications or blood transfusions in severe cases.
Anal Sac TumoursLumps appear as firm, deeper, masses underneath the rectum, where the anal sacs are located4.As tumours grow, it can compress the rectum and induce constipation4.
High rate of spread to other organs, can be fatal4.
Surgical removal or reduction of anal sacs, alongside with radiation and/or chemotherapy4.

 

Cats
TumourDescriptionRisksTreatment
Benign
LipomasRare in cats but also seen as soft, squishy, and moveable lumps just under the skin3.Usually remain benign, however large lipomas can impede mobility and cause discomfort3.No treatment is usually required3. However, if they grow significantly, surgical removal may be necessary3.
FibromaSimilar to dogs, appear as isolated, raised, hairless lumps that can either feel firm/rubbery or soft/squishy3.
They are growths of fibrous tissue such as muscle, blood vessels, fat3.
Usually remain benign but can grow and impede mobility and cause discomfort.
There is a malignant form, refer below to ‘Fibrosarcomas’3.
No treatment is usually required3. However, if they grow significantly, surgical removal may be necessary3.
Keratinised Skin CystsCan be solitary or multiple lumps, that are firm and hardened, and usually the same colour as the hair3. These lumps can be variable in size and are full of keratin3.If squeezed, can release keratin into adjacent areas and cause inflammation3.Surgical removal3.
Feline acneSmall bumps that typically develop on the chin, lips, and/or face2.Usually remain benign and can appear dirty.
Can become swollen and inflamed. If it becomes a chronic issue, harder, crusty, and painful lumps may develop2.
Improved hygiene: may include antibacterial shampoos, prescribed antibiotics (ointment or oral) from your veterinarian or oral antibiotics/steroids in more chronic cases2
Basal Cell TumourBasal cells are the topmost layer of the skin3. Common in older cats and longhair breeds3.
Appear as isolated, firm, and hairless lumps. Can be ulcerated. Variable in size (between 1-10cm) and often darker in colour3.
Cysts can result from basal cell tumours3. There is also a malignant form, refer bellow to ‘Basal Cell Carcinoma’3.Surgical removal3
Mast Cell TumoursUncommon in cats, usually found on the head and neck3.
Two forms:
  1. Mast cell type (more common): Appear as isolated, hairless lumps that range between 2-3cm3.
  2. Histiocytic type: most common in Siamese cats <4 years old3. Appear as multiple, small, firm lumps3.
If lumps on the skin are found to be mast cell tumours, usually benign3. But if lumps are found attached to internal organs using diagnostic imaging, poorer prognosis3.Surgical removal (mast cell type) or no treatment (histiocytic type) 3.
Malignant
LymphomaOne of the most common malignant tumours in cats, gastrointestinal form of lymphoma is the most common. Lumps can be found on the skin after the original tumour has spread3. If it originates from the skin, known as epitheliotropic skin lymphosarcoma, lumps can appear as itchy, crusty plaques3.High rate of spread to other internal organs/areas of the body – these forms are much more aggressive cancers3.
High rate of recurrence: Even if one lump is removed, there is a highly likely chance that another will occur3.
Dependent on the type of lymphoma, treatment can range from palliative care to surgical excision and/or radiation or chemotherapy3.
FibrosarcomaCommon soft tissue tumour in cats. Can appear lumpy, deep, and firm under the skin3.High rate of recurrence and spread3.Surgical removal followed with radiation or chemotherapy3.
Basal Cell CarcinomasCan appear as ulcers on head, legs, and/or neck. Not usually raised masses as seen in Basal Cell Tumours3.Can spread to other areas of the skin, causing more ulcers to form3.Surgical removal3.
Feline Injection Site SarcomaUncommon.
Variably sized lumps found on the back of the neck to shoulder region (where an injection would normally go)3.
Can develop years after injection occurred3.
Are highly aggressive tumours, requires advanced imaging pre-surgically to determine margins3.Surgical removal3.

Diagnosis of Lumps

Diagnosing lumps in dogs and cats typically involves a combination of an initial physical examination and further diagnostic tests. During the physical examination, your veterinarian will first assess the size, location (on the body and whether it is more superficial or deep), texture, and mobility of the lump; This allows for a general gauge of what kind of lump it could be.

If lumps are more superficial, the first diagnostic test to be taken would be a fine needle aspiration (FNA), this is performed by inserting a needle into the lump and drawing back the contents, whether it be tissue or fluid. Your veterinarian will then examine the sample on a slide via microscopic evaluation; just this step allows for the veterinarian to determine what type of lump it is, and whether it is benign or malignant. In some cases, a biopsy of the lump may be recommended to obtain a more comprehensive tissue sample. Additionally, imaging such as X-rays, ultrasound, or even CT scans, may be used to evaluate the extent of the lump, whether it has potentially spread to other areas of the body, and if the initial lump was deeper and FNA/biopsy was not possible.

If in-house microscopy/diagnostic evaluation of the lump is not possible or the lump is deeper and requires surgical excision, samples of the lump would be sent to a reference lab for a pathologist to evaluate its profile and results would be sent back to your veterinarian.

These initial diagnostic steps allow for accurate identification and the development of an appropriate treatment plan tailored to your fur baby’s needs

Importance of Accurate Diagnosis

Accurately diagnosing lumps is essential for ensuring the best possible outcome for your pet. Misdiagnosis or delayed diagnosis can lead to unnecessary treatments or missed opportunities for early intervention. Identifying the type of lump and its behaviour helps veterinarians craft a targeted treatment plan, minimising risks and maximising effectiveness. Accurate diagnosis also provides clarity and peace of mind for pet owners, helping them make informed decisions about their pet’s care.

Treatment Options

As evident in the tables above, treatment options chosen by a veterinarian are tailored to the type of lump present, which can vary significantly. To understand these treatment options further, it is important to recognise how the size, location, and aggressiveness of the lump can determine the most effective approach your veterinarian will follow.

  • Surgical Excision: A standard treatment for most lumps, especially malignant ones. For these cancerous tumours, achieving ‘clean margins’ is crucial. Clean margins involve removing the tumour along with a surrounding of healthy tissue to ensure all cancerous cells have been eliminated. The required margin size depends on the type and aggressiveness of the tumour and your veterinarian will discuss this with you beforehand. For example, mast cell tumours typically require wider margins (due to their behaviour of metastasising) compared to benign lipomas. It is important to note that surgical excision may also lead to aesthetic side effects such as scarring or asymmetry in the area of removal. Your veterinarian will discuss these possibilities with you during the planning stage.
  • Radiation Therapy: Is often used in conjunction with surgery for malignant lumps. It uses high-energy beams that targets the cancerous cells at the site of a specific tumour or lump post-surgery. However, radiation therapy can cause side effects such as skin irritation, hair loss in the treated area, or fatigue in your pet. These side effects are usually temporary and can be managed with supportive care.
  • Chemotherapy: Is also often used in conjunction with surgery for malignant lumps or when tumours are unable to be fully removed. Comparatively to radiation, it is used more for systemic cancers, such as lymphomas; Chemotherapy is the intravenous administration of cytotoxic medications that target cancer cells throughout the body. Chemotherapy can also reduce tumour size prior to surgery. While effective, chemotherapy can cause side effects such as nausea, loss of appetite, and lethargy. Your veterinarian will work to minimise these effects and ensure your pet’s comfort during treatment.
  • Medication and Supportive Care: Antibiotics and anti-inflammatory medication are often used for infected lumps and abscesses. Pain management and nutritional support are also critical for pets undergoing cancer treatment. In some cases, palliative care becomes the primary focus. Palliative care aims to manage pain, enhance comfort, and maintain the quality of life for pets with terminal conditions or when curative treatment is not an option. The decision to pursue active treatment or opt for palliative care is ultimately up to the pet owner, weighing the potential benefits of treatment against its impact on the pet’s quality of life.

Post-treatment, your veterinarian will most likely recommend regular monitoring to ensure there is no recurrence. This can include periodic imaging or aspirates of the surgical site.

While these treatment options may seem intimidating or overwhelming at first, your veterinarian is there to guide you through the process and make the journey for your pet and yourself as smooth and manageable as possible. Additionally, having pet insurance can help ease the financial burden of treatment, ensuring you can focus on making the best decisions for your pet’s health and quality of life, while enjoying your own peace of mind.

Cost of Diagnosis and Treatment

The cost of treating lumps in pets can vary significantly depending on factors such as the type of lump, the diagnostic tests required, and the complexity of the treatment course. For instance, fine needle aspiration, can be done during a consult, and (excluding cost of consult) may range from $100 for FNA, around $500 for imaging, to over $2500 for surgical excision, depending on the location.

Prevention Tips (Where Applicable)

While many lumps cannot be prevented, here are a few steps that can be taken to monitor and prevent when possible:

  • Regular Grooming & Skin Checks: Inspect your pet’s skin during grooming or cuddle sessions to catch lumps early.
  • Healthy Diet & Exercise: Maintaining a healthy weight can lower the risk of lipomas and other health issues, such as joint disease.
  • Parasite Prevention: Use flea, tick, and mosquito preventatives to reduce the risk of bites and related lumps.
  • Timely Vaccinations: Some lumps, such as post-vaccination nodules, are normal but ensuring proper vaccination schedules is crucial for the overall wellbeing and health of your pet.

When to See a Vet

Knowing when to consult your veterinarian is crucial. Schedule a visit if:

  • You notice single or multiple lumps appearing over a short period of time
  • The lump grows rapidly or changes in appearance (e.g. colour, texture, or size)
  • It causes obvious discomfort to your pet
  • There are signs of infection, such as redness, swelling, odour, or discharge
  • The lump is hard, immoveable, or feels deeper than just under the skin
  • Your pet shows other symptoms, such as lethargy, loss of appetite, diarrhoea, or weight loss

Your veterinarian may perform a fine needle aspiration, biopsy, or imaging to diagnose the lump and recommend the best course of action from there. Remember, no concern is too small or silly; veterinarians take all their clients worries seriously and are there to support you and your pet. Furthermore, having pet insurance can provide reassurance and help manage the financial aspects of care, allowing you to focus on your pet’s health with confidence.

Final Remarks

Finding a lump on your dog or cat can be stressful but remember that many lumps are harmless. By understanding the differences between benign and malignant lumps, recognizing the treatment options available, and staying vigilant about monitoring changes, you can navigate this journey with greater confidence.

Modern veterinary care offers advanced diagnostic tools, and a wide range of treatments tailored to your pet’s specific needs. From simple procedures for benign growths to comprehensive plans for more serious conditions, the goal is always to improve your pet’s health and comfort. Additionally, tools like pet insurance can help reduce financial stress, allowing you to focus on what matters most—your pet’s well-being.

Regular grooming and frequent skin checks can help you identify any new lumps early, giving you the best chance of addressing potential issues before they escalate. Open communication with your veterinarian is key; they are your partner in ensuring your furry friend receives the best care possible. Together, you can create a plan that fits your pet’s needs and lifestyle, whether it involves treatment, monitoring, or palliative care.

By staying informed, proactive, and dedicated to your pet’s health, you can provide them with a long, happy, and comfortable life. Every tail wag, soft purr, and shared cuddle is a testament to the love and care you give them—and the strong bond you share.

References

  1. Villalobos AE. Tumors of the Skin in Dogs [Internet]. Rahway (NJ): MSD Veterinary Manual; [revised 2018 Jun; cited 2025 Jan 22]. Available from https://www.msdvetmanual.com/dog-owners/skin-disorders-of-dogs/tumors-of-the-skin-in-dogs
  2. Weir M. Chin acne in cats [Internet]. VCA Animal Hospitals. [cited 2025 Jan 22]. Available from: https://vcahospitals.com/know-your-pet/chin-acne-in-cats#
  3. Villalobos AE. Tumors of the Skin in Cats [Internet]. Rahway (NJ): MSD Veterinary Manual; [revised 2018 Aug; cited 2025 Jan 22]. Available from https://www.msdvetmanual.com/cat-owners/skin-disorders-of-cats/tumors-of-the-skin-in-cats
  4. Weir M. Anal Sac Tumours [Internet]. VCA Animal Hospitals. [cited 2025 Jan 22]. Available from https://vcahospitals.com/know-your-pet/anal-gland-tumors
  5. Williams K., Llera R., Ward E., Hematoma of the Ear in Dogs [Internet] VCA Animal Hospitals. [cited 2025 Jan 22]. Available from https://vcahospitals.com/know-your-pet/hematoma-of-the-ear-in-dogs
  6. Grzyb K., Kleszynski B., Cat Skin Lumps, Bumps, and Cysts [Internet]. petMD; [updated 2024 Aug 28; cited 2025 Jan 22]. Available from https://www.petmd.com/cat/symptoms/cat-skin-lumps-bumps-and-cysts
  7. Jones L. Hemangiosarcoma in Dogs [Internet]. petMD; 2022 Jun 13. Available from https://www.petmd.com/dog/conditions/cancer/hemangiosarcoma-dogs
Annie | Pet Care Consultant and Pet Lover
As an independent writer with a Bachelor of Biomedical Science and a focus on insurance, Annie brings over 20 years of experience as a dedicated pet parent to her work. She aims to empower pet owners by providing valuable knowledge on pet insurance and strategies for maintaining their pets' well-being. With a deep commitment to the welfare of our furry companions, Annie strives to be a trusted source in the pet care community, offering expert insights to help owners make informed decisions for their pets.
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Specified Conditions includes:

  • Cruciate ligament damage
  • Intervertebral disc disease
  • Hip dysplasia
  • Patella luxation
  • Elbow dysplasia
  • Cherry eye
  • Entropion
  • Ectropion,
  • Osteochondritis dissecans (‘OCD’)
  • Lumps

Lumps means the protuberance or localised area of swelling or unusual growth that can occur anywhere on or in the body including tumours, warts, cysts, growths, mucoceles, haematomas and abscesses.

You can apply to reduce the 6-month exclusion period for Specified Conditions by using our request for Waiver Form. Simply take this form to your next vet visit and submit the completed form back to [email protected] within 14 days of the visit.

Optional Extra Benefits

During the application process You will be provided with the option to include Optional Extra Benefits that cover certain conditions and Treatments which are not otherwise covered under the Policy.

The Optional Extra Benefits are:

Alternative Therapies, Behavioural Problems, and Dental Illness.

Examples of Alternative Therapies: Acupuncture, physiotherapy, hydrotherapy.

Examples of Behavioural Problems: Excessive licking, fur pulling, pacing and destructive chewing.

Examples of Dental Illnesses: Dental diseases, gingivitis, periodontal disease.