Case: Kissy, a nine-year-old, female spayed Labrador Retriever presented to her local veterinarian for foul smelling breath. She had been previously healthy with the exception of a cranial cruciate rupture that had been successfully repaired when she was 7 years of age. Other than her foul breath she was clinically healthy. On examination, she was found to have moderate erythema of her gums diffusely, with moderate tartar. Based on a working diagnosis of stomatitis she was treated with a 14-day course of an antibiotic (clindamycin). Initially, she responded well with improvement of the odor from her mouth, but the gingival erythema did not improve. Over the next month, Katie’s red gums progressed and she developed an area on the external portion of her left lower lip, which was erythematous and ulcerated.
Given the progression of the lesion(s) the decision was made to biopsy the area on the lip. The biopsy revealed epitheliotropic lymphoma.
Epitheliotropic lymphoma is a form of lymphoma. However, instead of involvement of the lymph nodes, liver, spleen and bone marrow, dogs (and rarely cats) with this disease usually get a diffuse involvement of the skin, oral mucosa or both. On histopathology, malignant lymphocytes, usually, T-cells, infiltrate within the layers of the epithelium, either the skin or oral mucosa, which is why the disease usually starts as erythema and slowly progresses to plaques and nodules (Moore et al Vet Derm 2009). Eventually, the disease can spread to lymph nodes and to the peripheral blood. It is also known as mycosis fungoides.
The majority of dogs with epitheliotropic lymphoma have a diffuse form of the disease and chemotherapy using CCNU (lomustine) has been shown to result in responses in some dogs, but long-term control of the disease is uncommon with control times of 2 t o6 months published (Risbon et al, JVIM 2006, Williams et al JVIM 2006).
However, a subpopulation of these dogs will have involvement of the oral mucosa only. In these cases, radiation therapy may also be of benefit as it may be effective against the local tumor. Radiation therapy for this disease can involve either a definitive protocol involving 15 to 20 treatments delivered daily, or palliative radiation involving between 3 and 6 treatments over a three week period. Typically the radiation will need to be directed to large portions of the mouth, so side effects can be significant. However, these side effects can be managed well with anti-inflammatory and pain medications. Palliative protocols usually result in much less significant side effects.
Tumor control with radiation is not well defined yet and there are no true reports of the effectiveness that have been published.
However, local tumor control following radiation is very common with long-term tumor control in some dogs.
Kissy was treated with a course of palliative radiation involving 6 treatments delivered twice a week to the oral cavity and the local lymph nodes. Moderate erythema developed within the radiation field but resolved within 2 weeks of the end of treatment. Her owners decided not to pursue chemotherapy based on concerns about her quality of life.
The area of erythema and ulceration resolved following radiation and has been in remission for approximately 6 months.
Submitted by Dr. John Farrelly DVM, MS,
ACVIM (Oncology), ACVR (Radiation Oncology)
Radiation Oncologist/Medical Oncologist at The Veterinary Cancer Center
Moore PF, Affolter VK, Graham PS, Hirt B. Canine epitheliotropic cutaneous T-cell lymphoma: an investigation of T-cell receptor immunophenotype, lesion topography and molecular clonality. Vet Dermatol. 2009 Oct;20(5-6):569-76.
Risbon RE, de Lorimier LP, Skorupski K, Burgess KE, Bergman PJ, Carreras J, Hahn K, Leblanc A, Turek M, Impellizeri J, Fred R 3rd, Wojcieszyn JW, Drobatz K, Clifford CA. Response of canine cutaneous epitheliotropic lymphoma to lomustine (CCNU): a retrospective study of 46 cases (1999-2004). J Vet Intern Med. 2006 Nov-Dec;20(6):1389-97.
Williams LE, Rassnick KM, Power HT, Lana SE, Morrison-Collister KE, Hansen K, Johnson JL. CCNU in the treatment of canine epitheliotropic lymphoma. J Vet Intern Med. 2006 Jan-Feb;20(1):136-43.