Retinoblastoma in a dog
N. A. Syed, T. M. Nork, G. L. Poulsen, R. C. Riis, C. George and D. M. Albert
Department of Ophthalmology and Visual Sciences, University of Wisconsin, Madison, USA.
OBJECTIVE: To describe and classify a retinal tumor found in a dog that
histologically resembles human retinoblastoma and to discuss the molecular
mechanisms of retinal oncogenesis. METHODS: A dog eye with a retinal tumor
was examined histologically. Studies including immunocytochemical analysis
for retinal S-antigen and glial fibrillary acidic protein, enzyme
histochemical analysis for carbonic anhydrase, and nick-end DNA labeling
were used to characterize the tumor. Normal retina from another dog and
other tumors from dogs, including 2 ciliary body medulloepitheliomas and a
brain medulloepithelioma, were examined as controls. RESULTS: The retinal
tumor disclosed characteristics typical of human retinoblastoma, including
Flexner-Wintersteiner rosettes. It showed strong immunoreactivity with
S-antigen and glial fibrillary acidic protein. Carbonic anhydrase activity
also could be shown in the tumor. Apoptosis was found to be the predominant
method of cell death as shown by nick-end DNA labeling. In contrast to the
other tumors examined, this tumor contained areas with retinal
photoreceptor and glial differentiation. CONCLUSIONS: The histopathologic
findings and differential staining characteristics in this retinal tumor
are compatible with retinoblastoma, making this, to our knowledge, the
first documented case of spontaneous retinoblastoma in an animal.
