Central nervous system metastasis of a cutaneous epitheliotropic lymphosarcoma in a dog.

This report describes an uncommon case of a cutaneous epitheliotropic T-cell lymphosarcoma with central nervous system (CNS) manifestations in a 9-year-old mixed breed German shepherd dog. The animal had a history of sudden blindness, pyrexia and multifocal areas of hyperaemia in the oral mucosa. A biopsy from the muco-cutaneous junction of the lips led to the diagnosis of an epitheliotropic lymphosarcoma and the animal was humanely destroyed. At necropsy, hyperaemia in the oral mucosa was no longer detectable. In the brain, a mass effacing the optic chiasm and invading the hypothalamic area was found; histological examination revealed lymphoid tumour cell infiltration. In the epithelium of the oral mucosa, intra-epithelial lymphoid tumour cells, sometimes arranged in small clusters (Pautrier's microabscesses), in combination with a mild inflammation in the superficial dermis were observed. Skin and brain tumour cells expressed CD3 antigen, indicating their T-cell origin. This is, to our knowledge, the first report of a cutaneous epitheliotropic lymphosarcoma with CNS metastasis in a dog.