Mediastinal Lymphoma in dogs-
Mediastinal lymphoma in dogs usually develops in the lymphoid tissues of the chest. They are present around the cardiothoracic region. If left untreated, they can restrict the function of lungs, resulting in death.
This form of lymphoma comprises only a fraction of all cases of lymphosarcomas. It is typically characterized by enlargement of the cranial mediastinal lymph nodes, thymus, or both. Dogs suffering from mediastinal lymphoma encounter respiratory distress, polydipsia, polyuria, pitting edema of the head, necks and forelimbs.
It originates in the skin and can take the form of reddened lumps that can be itchy at times and also cause extreme discomfiture in dogs.
They appear as ulcers, nodules, plaques, ulcers, and erythremic or exfoliative dermatitis. In the early phases scaling, alopecia (loss of hair), and pruritus (itching) are seen. As the disease advances the skin becomes more erythematous, thickened, ulcerated, and exudative (relating to the oozing of fluid). There may also be oral involvement that can appear as multicentric erythematous, plaque like lesions or nodules on the gums and lips.
Diagnostic technique and clinical staging-
For cutaneous lymphoma, punch biopsies (3-4mm) should be taken from the most representative and infiltrated, but not infected skin lesions. Staging procedures vary and stage does not hold any prognostic importance.
The treatment of cutaneous lymphoma depends on the extent of the disease. Solitary lesions may be treated with surgical excision or radiation therapy. Fractionated radiotherapy has been associated with long term control. Diffuse non-T-cell lymphoma is best treated with combination chemotherapy. Retinoids, (chemical compounds related to Vitamin A) like isotretinoin (Accutane) and etretinate (Tegison) have yielded gratifying results in canine T-cell cutaneous lymphoma.
A combination of polyethylene glycol (PEG)-L-asparaginase, (30mg/kg given intramuscularly weekly) have proved to be effective on dogs with cutaneous T-cell lymphoma. However, remissions are not long-standing. Prednisone may also be useful in controlling pruritus. Studies have indicated that pegylated-liposomal doxorubicin (Doxil) has produced remissions. As a basis of experimental studies dogs were treated with CCNU (50 mg/m2 given orally every 3 weeks).
Mechlorethamine (Mustargen) can be applied on the skin as an aqueous solution or an ointment base. The solution is prepared by mixing 10 mg of mechlorethamine with 50 ml of tap water. For preparing 900 mg of ointment, 90 mg of mechlorethamine is mixed with 10 ml of absolute alcohol and sufficient xipamide (Aquaphor). It is essential to remove hair before applying the ointment. Gloves must be used, since mechlorethamine is carcinogenic (cancer causing) and can cause contact hypersensitivity in humans.
Dogs suffering from canine T- cell lymphoma were treated successfully with Isotretinoin for upto 13 months. Dogs treated with Doxil have been found to produce remissions in 40% cases. Although most of these were short-lived responses, remissions of 1 year or longer have occurred. Dogs treated with CCNU showed complete response and two of those responses were relatively durable (7 and 15 months). Dogs with diffuse T-cell lymphoma under the impact of combination chemotherapy with cyclophosphamide, vincristine, cytosine, arabinoside and prednisone (COAP) attained a median remission duration of longer than 250 days and a median survival of longer than 399 days. However, COAP may not have much of an effect on some dogs, as this study reveals.
Other Types of Lymphoma in dogs:
Other Articles of Interest:
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Tumors in Domestic Animals- Donald J. Meuten, DVM, PhD, is a professor of pathology in the Department of Microbiology, Pathology, and Parasitology at the College of Veterinary Medicine, North Carolina State University, Raleigh
Withrow and MacEwen’s Small Animal Clinical Oncology– Stephen J. Withrow, DVM, DACVIM (Oncology), Director; Animal Cancer Center Stuart Chair In Oncology, University Distinguished Professor, Colorado State University Fort Collins, Colorado;
David M. Vail, DVM, DACVIM (Oncology) Professor of Oncology, Director of Clinical Research, School of Veterinary Medicine University of Wisconsin-Madison Madison, Wisconsin