Skin Lumps and Masses

Whenever a lump or mass appears on/or beneath the skin of a cat, five possibilities exist as to its source:

  1. An abscess
  2. A hematoma or seroma
  3. A cyst
  4. A granuloma
  5. A tumor

Obviously, because the cause can vary, owners will need to employ the help of a veterinarian for identification of the mass. A fine-needle aspirate of the mass or an actual biopsy sample will assist the vet in a diagnosis.


Abscesses are usually painful to the touch and are often associated with other signs, such as fever, depression, and loss of appetite. They also tend to be fluctuant when direct pressure is applied to them. Abscesses are seen in cats more often than dogs.

Hematomas and Seromas

Hematomas and seromas result from leakage of blood or serum, respectively, from damaged blood vessels. Traumatic blows to the skin can result in hematoma or seroma formation beneath the affected area of skin.

The swellings caused by these lesions are also fluctuant, and because of the traumatic nature of their occurrence, they can be painful as well. In most cases, the swellings caused by hematomas and seromas will resolve on their own with time, assuming that infection does not occur in the meantime.


A cyst is simply a well-defined pocket filled with fluid, secretion, or inflammatory debris. Unlike abscesses, cysts are seldom painful to the touch. Sebaceous cysts or epidermoid cysts develop within the skin of cats when the sebum normally formed within sebaceous glands is not allowed to escape.

Sebaceous cysts can arise in multiple locations over the body of these cats, and can constantly recur throughout the life of the pet.

Although they pose no specific danger to the health of a cat, extra large cysts should be surgically excised.


Granulomas are firm, raised masses consisting chiefly of inflammatory cells sent to the particular area by the body in response to skin penetration by a foreign substance or infectious agent.

In essence, the body attempts to quickly surround and wall off the foreign invader before it can spread to other parts of the body.

Thorns, insect stingers, vaccines, fungal organisms, and certain bacteria are only a few of the things that can trigger granuloma formation. If a pet develops one of these growths, an attempt should be made to determine the cause of its appearance.

If an infectious agent is suspected, appropriate antimicrobial therapy is warranted to prevent further development of the granuloma. Granulomas might recede with time, depending on the cause. In some cases, surgical removal of the mass gets rid of the unsightly lump and its cause all at the same time.


Skin tumors or cancers can appear in a variety of types, sizes, and shapes. Common tumors that might appear as a lump or mass on or beneath the skin include sebaceous adenomas, lipomas, carcinomas, fibrosarcomas, and mast cell tumors.

It is imperative that a biopsy is performed in all instances to determine whether the tumor is malignant. Sebaceous gland tumors are among the most prevalent of all skin tumors in cats. They can appear anywhere on the body, including the eyelids.

The vast majority of these growths are benign and cause no problems whatsoever, unless they become traumatized as a result of sheer size. Excision of these tumors is curative locally, but others often appear elsewhere with time. Lipomas are benign, soft, fatty tumors that often form beneath the skin of cats and cause noticeable lumps.

They occur with greater frequency in older dogs that have weight problems. Although a diagnosis of lipoma might seem obvious, a fine-needle aspirate should always be performed to rule out the presence of its less common malignant counterpart, liposarcoma.

Lipomas can be surgically removed, yet because they can infiltrate into the muscle bundles and surrounding tissue, this removal might be unknowingly incomplete and the tumor might recur.

As a result, many practitioners will choose to remove only those lipomas that are extralarge or those diagnosed as malignant. Fibrosarcomas in cats have been known to occur infrequently after certain vaccines are administered.

As a result, any lump that appears 2 to 6 weeks following vaccination should be brought to the attention of a veterinarian. Mammary tumors are relatively common in intact dogs. Treatment involves surgical removal of the affected gland(s).

For extensive tumors, chemotherapy might also be employed. It is imperative that a biopsy be performed on all firm lumps to determine whether or not a tumor exists.