What are lymphocytes?
Lymphocytes are a type of white blood cell that play an important role in the immune system by defending the body against disease. Generally, there are two types of lymphocytes: T lymphocytes and B lymphocytes. Each plays their own role in the immune system. Lymphocytes are found all over the body, including the skin. Certain areas of the body (called lymphatic tissues) are rich in lymphocytes. One such area are the lymph nodes.
What is lymphoma of the skin?
Lymphoma of the skin (or cutaneous lymphoma) is an abnormal replication of lymphocytes that form nodules, plaques, or other lesions within the skin. There are many forms of lymphoma. The following forms are the most common:
- epitheliotropic lymphoma
- dermal lymphoma
What causes this cancer?
The reason why a particular pet may develop this, or any tumor or cancer, is not straightforward. Very few tumors and cancers have a single known cause. Most seem to be caused by a complex mix of risk factors, some environmental and some genetic or hereditary. In the case of cutaneous lymphoma, no specific risk factors or cause have been identified.
What are the signs of cutaneous lymphoma?
The signs of cutaneous lymphoma vary, depending on the type of lymphoma and where it is located. Generally, cutaneous lymphoma can appear as various-sized irritated, ulcerated, or infected patches anywhere on the skin. It can especially affect the gums, nose, or lip margins (where the lips meet the skin). These areas may become ulcerated (break open) and bleed or crusted, and secondary infections are possible. This can cause your pet some oral discomfort and/or reluctance to eat.
"The signs of cutaneous lymphoma vary, depending on the specific type of lymphoma and where it is located."
Epitheliotropic lymphoma is the more common form of cutaneous lymphoma. It can look like nodules, plaques, or scabs on the skin. The lesions are usually dry and scaly, with flaking and hair loss (alopecia). Epitheliotropic lymphoma is made of T-cell lymphocytes.
T-cell lymphocytes can produce a protein that causes a higher than normal calcium level in the blood (called hypercalcemia). Pets with hypercalcemia may drink and/or urinate more, and kidney damage is possible. They can also feel quite ill and show signs of vomiting or diarrhea when their calcium levels are too high.
Dermal lymphoma, which is less common, typically appears as nodules on the skin. Many areas may be affected.
How is this cancer diagnosed?
The easiest way to determine if lymphoma is present is by biopsy of the skin. However, if nodules are present (or lymph nodes affected), a fine needle aspiration may be performed.
Fine needle aspiration (FNA) or biopsy will be performed. FNA involves taking a small needle with a syringe and suctioning a sample of cells directly from the tumor and placing them on a microscope slide. A veterinary pathologist then examines the slide under a microscope.
With lesions that are progressive (continuing to grow) or return after surgery, biopsy is usually the most definitive way to obtain a diagnosis. A biopsy is a surgical excision of a piece of the tumor. Pieces of the tumor are then examined by a veterinary pathologist under the microscope. This is called histopathology. Since lymphocytes are naturally present in the skin, and especially present with inflammation and infection, biopsy with histopathology is the most accurate way to make a definitive diagnosis of cutaneous lymphoma.
How does this cancer typically progress?
Regardless of the form of lymphoma, there may be multiple lesions present on your pet's body. These can grow and become increasingly bothersome. They can also spread to other areas of the body, including the lymph nodes (especially those in front of the shoulders, in the armpits, between the legs, and behind the back legs) and the abdominal organs.
What are the treatments for this type of tumor?
By far, the most common treatment for cutaneous lymphoma is chemotherapy. Unfortunately, the response to treatment, although initially encouraging, is typically short-lived, with gradual return of the tumors. If your pet no longer responds to therapy, your veterinarian will discuss alternative chemotherapy options or supportive care protocols.
In dogs that develop only a single, localized lesion (rare, although reported), radiation therapy may be helpful, as it has shown good success in humans.
Is there anything else I should know?
Given that the lesions of cutaneous lymphoma involve the skin, may be readily accessible, and can become bothersome, your pet may be tempted to lick, chew, or scratch. Your pet should not be allowed to lick, chew or scratch any of the affected areas. Prevention of self-trauma is key to managing pets with this disease.
Secondary infection is common with cutaneous lymphoma. This alone can cause significant discomfort for your pet. Your veterinarian may prescribe antibiotics as necessary. If oral lesions are present, they may become dry, cracked and painful, and your pet may be reluctant to eat. Pain medications may be recommended.