Expression of the photoreceptor-specific S-antigen in human retinoblastoma.

This work presents an immunofluorescent study of the distribution of the photoreceptor-specific S-antigen in human retinoblastoma, using mouse monoclonal antibodies. Three cases of differentiated retinoblastoma displayed S-antigen immunoreactivity with various patterns of labeling which depended on the degree of differentiation of the area studied. Flexner-Wintersteiner rosettes and fleurettes were labeled only with monoclonal antibody S2D2, whereas undifferentiated areas were labeled with four different anti-S-antigen monoclonal antibodies, including S2D2. On the other hand, the three undifferentiated retinoblastomas did not show any labeling with these antibodies. The presence of S-antigen in differentiated retinoblastoma confirms that the origin of this tumor is from the photoreceptors, but the question remains unanswered for undifferentiated retinoblastoma for which another origin--glial or primitive neuroectodermal cells--may be proposed.