Immunohistochemical studies of retinoblastoma.

Various immunohistochemical markers were detected in 27 cases of human retinoblastoma by immunohistochemical avidin-biotin-peroxidase complex and peroxidase-antiperoxidase techniques using mono- and polyclonal antibodies. The glial markers, glial fibrillary acidic protein and Leu-7, were detected in the natural retinal component and perivascular glial cells within the tumor mass. In 4 among 27 cases Leu-7 was positive in the glial cells which were interspersed randomly among tumor cells and not associated with blood vessels. The neural marker, neuron-specific enolase, stained strongly positive in undifferentiated tumor cells and weakly positive in rosettes and fleurettes in most of the cases (21/27). Opsin, the photoreceptor marker, which is present only in the outer segment of photoreceptor cells, was detected in tumor cells of fleurettes in one case and also in rosettes in 6 cases. These results support the view that retinoblastoma has a predominantly neuronal nature with significant photoreceptor-like differentiation and rarely glial differentiation.