Epitheliotropic lymphoma affects both back feet of this boxer. Photo by Dr. Jeff Chemelewski
(also known as cutaneous T cell lymphoma and cutaneous epitheliotropic lymphoma)
Lymphoma can arise in any organ that contains lymph tissue (which turns out to be just about anywhere in the body). While lymphoma generally occurs in lymph nodes and in organs with substantial lymphatic system presence, occasionally lymphoma arises in the skin. Skin forms of lymphoma are often itchy and rashy and thus are readily mistaken for allergic dermatitis. Superficial skin infections are common with skin lymphoma as well as with most other dermatitis cases, which compounds the difficulty in making the correct diagnosis. Biopsy is needed to get the correct diagnosis.
There are three types: mycosis fungoides, Sézary syndrome, and pagetoid reticulosis.
This sounds like it should be a benign fungal infection, but unfortunately it is a malignant cancer so named because the skin tumors are thought to resemble mushrooms. As mentioned, it can look like a skin infection with nodules and frequently goes unrecognized until it fails to respond to the usual skin-oriented antibiotics and is biopsied.
An oral form also exists where the gums become inflamed and ulcerated. This could also be mistaken for any number of oral diseases and, again, a biopsy is needed to find the truth.
Sézary Syndrome (A Rare Complication)
Mycosis fungoides can progress to what is called Sézary syndrome. Here, the skin cancer advances into the bloodstream to create leukemia. The cancer cells in the blood are not like other leukemia cells and are called Sézary cells. This complication almost never happens in dogs but happens in approximately 5 percent of humans with mycosis fungoides, so the term may come up if you do any internet research.
The only difference between pagetoid reticulosis and mycosis fungoides is seen on biopsy. Pagetoid reticulosis is a more superficial form of skin lymphoma which does not penetrate to deeper skin structures. It can be localized to one area of the skin or to large areas of skin.
Most pets succumb to euthanasia when there are too many ulcerated growths, too much intractable itching, or the infections cannot be controlled. Variable survival times have been reported in different studies but prognosis is generally regarded as poor, while a good goal is 6 months for dogs and perhaps 10 months for cats. (This contrasts to the human form of the disease, which is much more readily controlled with chemotherapy.) For many patients, the goal of chemotherapy is not to achieve a longer survival but to improve life quality during a relatively short survival.
Epitheliotropic Lymphoma, Dog (Photograph)
Epitheliotropic lymphoma in a French bulldog. Photo by Dr. Neal Saslow.
Aside from chemotherapy, a few less conventional methods have emerged.
Skin lymphoma cells appear to have receptors for synthetic vitamin A derivatives. Median survival times have been increased with retinoids.
The Hollywood brand of safflower oil (apparently the Hain brand does not work) was given to 6 out of 8 dogs who had lost remission from conventional treatment and were able to achieve remission with no other therapy.
This is a new medication recently approved for lymphoma treatment in dogs. When combined with prednisolone, 45 percent of dogs with this condition achieved at least partial remission.