Mycosis fungoides
Canine epitheliotropic cutaneous lymphoma (ECL) is a tumor of skin and mucous membranes that occurs in old dogs (mean age 11 years) and has no breed predilection. The lesions evolve from a patch-plaque stage into a tumor stage in which distant metastasis is observed. There are two forms of the disease: cutaneous (involves skin) and oral.
Epitheliotropic lymphoma is also known as mycosis fungoides (MF), so named because of the mushroom-like appearance of the tumors in humans. This term is considered archaic and confusing (being confused with mycotic {fungal] skin disease).
As early signs of MF may also occur in many other diseases, the condition is often referred to as great impersonator. In dogs and cats, four clinical forms have been described. Many dogs present with signs of itchiness, skin inflammation and seborrhea that do not respond to treatment. Other animals can develop ulcerations on the footpads and in the mouth.
Early stages of epitheliotropic lymphoma can resemble inflammatory skin disease including inflammation, scaling and itch. Itchy skin and scaling represent the early stage of (ECL) which then progresses to plaques over a period of several months. At this stage of the disease, dogs become depressed, lethargic, have fever and lose appetite. Depigmentation, alopecia, plaques, ulceration, and crusting develop. Many dogs are presented with a history of chronic skin disease. The skin lesions may be localized in one place of the body or generalized. Dogs presented with advanced epitheliotropic lymphoma usually have multiple tumors that can occur anywhere, but appear to have a predilection for mucocutaneous junctions and the oral cavity. Metastasis to lymph nodes and other organs occurs, so dogs may present with other signs of systemic disease.
The prognosis is poor for both forms of cutaneous lymphoma. Recurrence of disease is very common despite various treatments. Generalized epitheliotropic lymphoma is often treated with a five-drug chemotherapy. Palliative therapy, such as glucocorticoid and antibiotic administration as well as antiseborrheic and antibacterial shampoos, can temporarily improve the patient's quality of life. Radiation treatment may be helpful, with or without systemic chemotherapy, depending on the stage of disease. However, there is no evidence that the therapies extend the lifespan of a dog diagnosed with mycosis fungoides. Retinoid therapy has been used but with unpredictable success. Surgical removal of the tumors is impossible because such extensive areas of the body are usually involved.
Adapted from
1. Elizabeth A. Nesbit, DVM; Perry J. Bain, DVM, PhD; Nicole C. Northrup, DVM, and Kenneth S. Latimer, DVM, PhD. Canine Round Cell Tumors
2. Bernard F. Feldman, Joseph G. Zinkl, Nemi Chand Jain. Schalm's Veterinary Hematology
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