May 2005

Lymphosarcoma: Equine Cancer

It’s a common cancer with a poor prognosis.

Cancer is relatively rare in horses. However, one of the most common equine types is called lymphosarcoma, a serious cancer with a poor prognosis. This is a cancer of the lymphatic system, lymphocytes in the internal forms and histiocytes in some cases with the skin form. The disease may take several forms, each with different signs:

• Cutaneous: This form appears as lumps under the skin. They may be single or multiple. These lumps usually stay covered with skin and hair but may ulcerate through the skin. The masses may be mistaken for hives, bite/sting reactions or benign tumors. As time goes on, local lymph nodes become enlarged and the tumors…