An 8 year old gelding with various and non specific clinical findings namely: depression, poor body condition, oedema, tachycardia, dehydration, lameness, leukocytosis and neutrophilia. Despite several complementary examinations a definitive diagnosis cannot be made. Owing to the worsening of clinical signs, the horse was euthanized. Histopathology reveals a cortical adenoma which helped explained the observed clinical findings. Reports of cortical tumours are rare in horses.