Skin Cancer in Dogs

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:

Cytology

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.

Biopsy

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.

A punch biopsy may be used when the lesions are near the surface of the skin. This type uses the same principle as a cookie cutter, and a small circle of skin is removed with an instrument called a punch. Multiple samples can be taken from different areas in order to increase the chance of making a diagnosis. This can be done with local anesthesia and/or sedation.

A needle biopsy can be used to take a core of tissue from a discrete mass – one that is in separate parts. This can be done with local anesthesia and/or sedation.

An incisional biopsy is one where only a part of the tumor is removed for evaluation. An incisional biopsy is performed when the tumor cannot be easily removed, when a malignant tumor is suspected or when there is already evidence of metastasis. It requires general anesthesia.

An excisional biopsy means that the entire tumor is excised or removed along with some margin of normal tissue. It requires general anesthesia.

Complete Blood Count (CBC)

A complete blood count is drawn to evaluate your dog's red blood cells, white blood cells and platelets.

Serum Chemistry Profile

A serum chemistry profile is drawn to evaluate your dog's overall health. If your animal 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.

Urinalysis

A urinalysis is another useful test to help evaluate your dog'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.

Special Stains

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.

Buffy Coat

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.