A seven year old Slovak warmblood gelding, used as a police horse, initially presented to the refferal clinic when it was five years old, with an itching keloid on the distal limb, requiring surgical removal. After surgical removal of the keloid and successful closure of the skin, it was necessary to maintain bandaging the healed wound to prevent self mutilation as the healed surgical site remained pruritic post operatively. After two years, the horse presented to the clinic again with pruritic and alopetic regions of the head, neck, limbs and base of the tail. Attempts to find the cause of dermal iritation included dermatological, parazitological, microbiological and ultrasonographic examination. Treatment with corticosteroids, antiparasitics and antibiotics were not succesfull. Further investigation due to the horse's worsening general status led to the finding of marked pleural effusion. Cytology of the pleural fluid confirmed there was, as suspected, neoplastic changes in the thoracic cavity. Furthermore there were gross pathological changes of the lymphatic tissue of the cranial mediastinum, surroundings of the aorta in the thoracic cavity and lymph nodes of the abdominal cavity. Histolology of the lymphatic nodes found poorly differentiated round cell tumours. Histopathological findings confirmed there was a very aggressive form of lymphoma. The pruritus, generalised moth-eaten alopecia and self-mutilation were the first symptoms of the terminal disease in this case.