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Imagine you are sitting on the couch with your beloved feline on your lap, and as you gently stroke their fur you feel a lump under the hair. What do you do? What is it? Can it be treated? There are many things that can cause lumps and bumps and the first step in answering these questions is for you to take your cat to the vet to get the lump checked.

Most common causes of lumps and bumps in cats

Skin infections

• Bacteria infections and abscesses – often due to infection introduced under the skin from another cat during fighting
• Parasitic skin diseases – ticks, mites
• Fungal skin diseases – Cryptococcus, Phaeohyphomyocosis
• Mycobacterial infections

Allergic and inflammatory diseases

• Allergies – flea allergies, food hypersensitivity, contact dermatitis, miliary dermatitis
• Eosinophilic granuloma disease including rodent ulcers
• Insect bite reactions
• Feline acne

Tumours and cancers

• Benign tumours such as lipomas
• Malignant cancers such as mast cell tumours, fibrosarcoma, squamous cell carcinoma, mammary gland tumour (breast cancer), haemangiosarcoma, lymphoma

Cysts

• Apocrine sweat gland cysts, sebaceous gland cysts, follicular cysts

How does my vet determine the cause of my cat’s lump?

After taking a careful history from you about the lump and your cat’s general health, your vet will then perform a thorough physical exam on your cat and inspect the lump closely. Some lumps such as abscesses can be diagnosed by examination alone, but the majority will require some further testing.

The most commonly performed initial test on a lump is a fine needle aspirate. For this test your vet will insert a needle into the lump to obtain a sample of cells that are then transferred onto a microscope slide. The slide is then placed in a fixative to preserve the cells and then stained with special dyes to help visualise the cell structure. The slide is air dried and examined under the microscope. In many instances a diagnosis can be made right away. For more complicated conditions, the slide may need to be sent to a specialist pathologist for a second opinion.

There are some conditions that are difficult to diagnose by a fine needle aspirate alone. This may be due to the lump’s tissue being too hard or fibrous making it hard for the cells to be aspirated through the needle such as with a fibroma or fibrosarcoma. Alternatively, there are some conditions that in order to make an accurate diagnosis, we need to see both the architecture around the cells as well as the cells themselves. For these lumps, a tissue biopsy is required. This is a short procedure performed under general anaesthetic. The tissue sample is fixed in formalin sent to the lab for histopathology testing by a specialist veterinary pathologist.

Treatment of lumps

Treatment of lumps or bumps will depend on the cause and may include:

• Surgical debridement – Abscesses need to be opened up, drained and possibly surgically debrided. A course of antibiotics and pain relief is usually given
• Surgical removal – Malignant tumours generally need surgical removal which may need to be followed by chemotherapy and/or radiation treatment (if available in your city). Many cancers will also require further “staging” to assess the extend of the disease. Benign tumours are generally cured by surgical excision provided adequate margins of normal tissue can be achieved.
• Careful monitoring – Not all cysts need surgical removal unless they rupture or become infection. Your vet is the best person to guide you on this decision.
• Other medications – various specific medications may be recommended after a diagnosis has been made. For example, allergic skin disease may require a course of anti-inflammatory drugs, flea control or specialised nutrition. Skin infections may require antibiotics or anti-fungal medications.