LYMPHOMA IN THE SKIN
(Cutaneous T Cell Lymphoma
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. Further compounding the difficulty in making the correct diagnosis is the fact that skin superficial skin infections are common not only in allergy situations but in many skin diseases including skin lymphoma so partial responses to antibiotics may be misleading. Lymphoma in the skin would be a rare cause of dermatitis but there has to come a point where biopsy is needed to explain a poor response to the usual therapies. Biopsy is needed to capture the diagnosis of lymphoma.

THREE TYPES:
MYCOSIS FUNGOIDES, SEZARY SYNDROME, AND PAGETOID RETICULOSIS

MYCOSIS FUNGOIDES
The name "mycosis fungoides" suggests a benign fungal infection but nothing could be farther from the truth. Mycosis fungoides is a very malignant form of skin lymphoma; it is named for fungus because the tumors are said 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.

Mycosis Fungoides with lots of nodules. (Photocredit: Neal Saslow DVM and Veterinary Information Network)

Same cancer but without the nodules it looks more like a bad infection. (Photocredit: Marina Siegert DVM and Veterinary Information Network)

Oral Mycosis Fungoides (Photocredit: Erin Trimmier DVM and Veterinary Information Network)

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, biopsy is needed to find the truth.

SEZARY SYNDROME (A VERY RARE COMPLICATION)
Mycosis fungoides can progress to what is called “Sezary 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 “Sezary cells.” This complication almost never happens in dogs but happens in approximately 5% of humans with mycosis fungoides so the term may come up if one conducts internet research.

PAGETOID RETICULOSIS
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.

PROGNOSIS

Most pets succomb 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, with 6 months for dogs and perhaps 10 months for cats, being a good goal. (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. Most studies report median survival times of 6-7 months.

TREATMENTS

Since most tumors arise in groups or involve large areas, surgery or radiotherapy is not going to be effective. Chemotherapy will be needed to reach all the tumors. This might be provided by a single medication like lomustine but could just as likely include a multi-drug combination protocol involving such medications as L-asparaginase, prednisolone, cyclophosphamide, vincristine and/or doxorubicin.

Aside from chemotherapy regimens a few less conventional methods have emerged.

• Retinoids
  Skin lymphoma cells appear to have receptors for synthetic vitamin A derivatives. Median survival times have been increased with retinoids. This all sounds good but the type retinoids used to treat such skin diseases also cause human birth defects and because of this, their access is highly regulated and they are very difficult to obtain in the U.S.
  
  
• Safflower Oil
  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. It should be noted that this was a very small study (only 8 dogs) and GI upset can result from the twice weekly oil doses needed for this therapy.
  
  
• Rabacfosadine
  This is a new medication recently approved for lymphoma treatment in the dog. When combined with prednisolone, 45% of dogs with this condition achieved at least partial remission.

Page posted: 4/5/2023
Page last updated: 5/26/2023