Primary and secondary tumours occurring simultaneously in the brain of a dog

Primary brain tumours of a single histological type and metastatic brain tumours are well described in dogs in the current veterinary literature. However, the concurrent presence of a primary and secondary tumour in the brain of a dog has never, to the authors' knowledge, been previously reported. The clinical and pathological features of a nine-year-old, female boxer with an oligodendroglioma and metastases from a mammary gland adenocarcinoma occurring simultaneously in the brain are described in this case report. Information in the veterinary literature on multiple malignancies affecting the central nervous system is very limited; therefore, a discussion about comparative situations in human medicine has been included.