both diagnosis and differential diagnosis will be conducted by the following criteria : age of animal , alterations caused by marek 's disease to nerves , eyes , and skin , tumour growth in bursa fabricii caused by lymphoid leucosis , atrophy of bursa fabricii caused by marek 's disease , as well as differences between both diseases regarding tumour development in other organs , with due consideration to be given to the number of affected organs , as a whole , and to pathologico-anatomic organic changes caused by tumour growth .
C0012634
diseases
C0027651
tumour