Overview of Feline Skin Cancer
Skin cancer encompasses a broad category of tumors that includes any uncontrolled growth of cells of the skin or associated structures such as glands, hair follicles and supportive tissues (fat and connective tissue). Metastasis (spread) to the skin from tumors elsewhere in the body can occur but these are not considered skin tumors because they did not start in the skin.
The skin is the second most common site of cancer in the cat. Skin tumors in cats are more likely to be malignant than those in dogs. Skin cancer frequently occurs in cats that are middle-aged to older (six to 14 years of age), although there are several types of skin cancers that occur in young cats. There are no breeds of cats that are more commonly affected with skin tumors than others.
The cause of the majority of skin cancers is unknown. Exposure to the sun has been shown to cause a higher incidence of two types of skin cancer: squamous cell carcinoma and hemangioma. Cats that are white and live outdoors have a high incidence of squamous cell carcinoma, particularly in parts of the body that have a thin haircoat such as the ears, nose and eyelids. The feline immunodeficiency virus (FIV) has also been linked to the development of squamous cell carcinoma in cats, although it is unclear what role the virus plays in the development of these tumors. There may be a genetic basis for the development of certain cancers.
Skin cancers can be divided into four different categories, depending upon the cell type that is involved. These categories are epithelial tumors, mesenchymal tumors, round cell tumors and melanomas.
In cats the most common tumors are basal cell tumors, squamous cell carcinoma, mast cell tumors and fibrosarcoma. Most skin cancers appear as a lump in or underneath the skin or as a sore that does not heal. Cats with skin cancer may experience discomfort or itchiness because of the cancer. This may cause them to chew or scratch at the affected area. With certain type of cancers there may also be redness to the skin or it may have a flaky appearance.
Diagnosis of Skin Cancer in Cats
Diagnostic tests are needed to recognize skin cancer and exclude other diseases. The ability to treat a skin cancer successfully depends upon the type of cancer and how advanced it is at the time of diagnosis. Tests that your veterinarian may wish to perform include:
Treatment of Skin Cancer in Cats
Treatment for skin cancer depends on the type of tumor that is present and how advanced the disease is at the time of diagnosis.
Home Care and Prevention
Examine your cat’s skin on a regular basis. If you note a new lump, a sore that does not appear to heal, or other changes in the skin seek veterinary attention as soon as possible.
After surgery monitor the incision for redness, swelling or discharge. Alert your veterinarian if any of these signs are noted.
Avoid prolonged exposure of your cat to sunlight. This is particularly important if your cat has light colored skin. If you have a white cat that likes to sit in windowsills, ask your veterinarian whether you should consider placing a sunscreen on her ear tips.
In-depth Information on Feline Skin Cancer
Immune Mediated Diseases
Several immune mediated diseases like systemic lupus and pemphigus can cause ulcers and sores in the skin that may look cancerous. The most common areas affected by immune mediated diseases include the tips of the ears, lips, nose and footpads.
In cats, there is a collection of diseases called the eosinophilic granuloma complex that can cause lumps in the skin that are frequently itchy, as well as areas of ulceration. It is suspected that the underlying cause of these diseases is an allergic reaction to either the food or something in the environment.
Several different types of cysts can be found in the skin and occur as a swelling that opens and drains intermittently. The fluid that comes from a cyst can be anywhere from a clear fluid to a thick “toothpaste” type material.
An injury to the skin can look like certain skin cancers. You should seek veterinary attention if a suspected injury does not heal within a reasonable amount of time.
Diagnosis In-Depth for Feline Skin Cancer
Veterinary care should include diagnostic tests and subsequent treatment recommendations. Diagnostic tests are needed to recognize skin cancer and exclude other diseases. Tests may include:
If there is a discrete mass, your veterinarian may recommend an aspirate of the mass. A needle is placed into the mass and suction is applied to collect some of the cells into the needle. These cells are then spread onto a slide an examined under the microscope.
Cytology is a quick, relatively non-invasive way to evaluate many skin masses. However, it should be noted that certain cancers are difficult to diagnose by cytology and a biopsy may be required. An aspirate can only sample a few cells so it may not be representative of the entire mass.
A biopsy is the most accurate way to diagnose a skin tumor. There are multiple ways to biopsy a suspected skin cancer. The type of biopsy will depend upon the location and size of the tumor as well as the overall health of your dog. It is essential that any skin mass that is removed be submitted for biopsy. A diagnosis of a benign tumor cannot be made without a biopsy. It is also important that all tissue that is removed be submitted, even if the tumor is large.
Complete Blood Count (CBC)
A complete blood count is drawn to help evaluate your cat’s overall health.
Serum Chemistry Profile
A serum chemistry profile is drawn to help evaluate your cat’s overall health. If your cat is to undergo anesthesia or receive radiation therapy or chemotherapy, it is important to know if there are underlying health problems that may complicate treatment.
A urinalysis is obtained to help evaluate your cat’s overall health.
Chest radiographs (X-rays)
A common location for metastasis or spread of a malignant cancer is the lungs. If a malignant skin cancer is diagnosed, your veterinarian will recommend chest X-rays to look for spread of the tumor. The presence of metastasis to the lungs will change the recommended treatment plan as well as make successful treatment less likely.
In some cases, it is difficult for the pathologist to determine the tumor type using only the stains that are routinely applied to the biopsy sample. Special stains may be required to identify the type of tumor. Your veterinarian and the pathologist will decide what special stains are needed based on the tumor types they are suspecting. These tests take extra time to complete and there is generally an added fee. However, they are important because the results may change both type of treatment and the prognosis.
A buffy coat is a blood test that looks for mast cells out in the bloodstream. Normal animals rarely have mast cells out in circulation. This test is requested only when a mast cell tumor is diagnosed.
Lymph Node Evaluation
Lymph nodes are another common site for metastasis. When a malignant skin tumor is diagnosed, the lymph node that is closest to that tumor is examined for spread of the tumor. This can be done either by an aspirate or biopsy of the lymph node.
Treatment In-Depth for Feline Skin Cancer
Treatment for skin cancer may include one or more of the following:
Surgery is the most commonly employed treatment of skin tumors. For benign skin tumors, surgery can be curative. For some malignant skin tumors, surgery can also be curative, although the chance of recurrence at the same site is higher because malignant tumors tend to be more invasive. Malignant tumors can also spread and surgery will have no effect on the potential for metastasis.
When removing a potentially malignant tumor, a wide margin of normal tissue needs to be taken as well as the tumor. Ideally, this margin should be 1 1/2 to 2 inches of normal tissue. In some locations, such as the leg or face, there may not be enough normal tissue that can be removed to ensure a wide excision. It should be expected that after a surgery for a malignant tumor that the incision is usually much larger than the original tumor.
Your veterinarian may biopsy the tumor before attempting to remove it. This is desirable in certain situations because it allows your veterinarian to determine how aggressive the surgery should be or whether surgery is the best option.
Radiation therapy is used in the treatment of several different types of skin cancer. The most common tumor types that are treated with radiation therapy include: mast cell tumors, malignant mesenchymal tumors (a family of tumors called soft tissue sarcomas) and squamous cell carcinoma. Radiation therapy is most effective when surgery can be performed to reduce the amount of tumors to microscopic levels. This means that the tumor is no longer visible.
Radiation therapy usually involves multiple treatments given over several weeks. Each treatment requires a brief period of anesthesia since animals cannot move during their treatment. The most common side effects associated with radiation therapy are changes in the skin, such as redness of the skin, hair loss, oozing of the skin, which heal after the completion of radiation therapy.
If your veterinarian feels that radiation therapy may be helpful to your pet, he will refer you to a facility that has radiation therapy available.
The use of chemotherapy in the treatment of skin tumors is limited to certain situations. Chemotherapy may be recommended if the tumor has already metastasized, if there is a high potential for metastasis or if other treatments are not possible. The most common tumor types for which chemotherapy is recommended are lymphosarcoma and mast cell tumors.
The type of drugs used, the frequency at which they are administered and the length of treatment will depend upon several different factors, including: the type of tumor, whether the tumor was removed and if there are any metastases already present.
Chemotherapy is well tolerated in both cats and dogs and the risk of serious side effects is low. The most common side effects include gastrointestinal symptoms, such as vomiting, diarrhea, and loss of appetite, or a drop in the white blood cell count.
Cryosurgery involves the use of liquid nitrogen to freeze the tumor. Tumor cells that are frozen will die so cryosurgery can be used to treat tumors. This type of therapy is not frequently used. It should be noted that recurrence of many tumors is likely because of the inability to kill the cells at the edges without having serious effects of healthy tissue.
This new therapy can be used to treat certain types of skin cancer. It is used most frequently for the treatment of squamous cell carcinoma on the ears and nose of cats. It involves giving the patient an intravenous drug and then exposing the tumor to laser light. The drug sensitizes the tumor to the laser light and thus the tumor is killed. This type of therapy can be effective, but it requires special equipment and can leave animals sensitive to light for a period of time after treatment.
Examine your cat’s skin on a regular basis. If you note a new lump, a sore that does not heal or other changes in the skin, seek veterinary attention.
If your cat has surgery as part of the treatment of his skin cancer, he may need some additional care. Cats that have had surgery should be kept quiet for the first two weeks to prevent tension on the incision. The incision should be monitored for redness, swelling or discharge. It is important to keep your cat from licking or chewing at the incision because this can cause the incision to come apart. If there are sutures or staples, these will need to be removed approximately two weeks after surgery.
The surgery site should be evaluated on a frequent basis to detect any cancer recurrence. If recurrence is suspected, it should be brought to your veterinarian’s attention immediately. Retreatment is more likely to be successful if the tumor is still small.
There is no known cause for the majority of skin cancers so prevention is difficult. Exposure to sunlight should be limited especially for white or light colored cats.