IMMUNOCYTOCHEMICAL FEATURES OF RETINOBLASTOMA IN AN ADULT

Objective: To describe the clinical course and immunocytochemical char acteristics of an unusual intraocular tumor. Methods: Immunocytochemic al analysis of the enucleated eye with an intraocular mass that marked ly waxed and waned in size during 1 year of close observation of a 29- year-old woman. Results: Most of the tumor was composed of either dyin g or rapidly proliferating cells. One area located near the retina con sisted mostly of well-differentiated cells in uniform sheets (bacillet tes) with lacelike glial processes between the tumor cells. Almost all of the differentiated tumor cells were positive for S antigen. In par ticular, the dominant cell type stained positively for both antibodies known to be specific for those isoforms oi S antigen found only in bl ue cones and rods but not in red or green: cones. Only a few of these cells labeled positively with an anti-rhodopsin antibody. Conclusions: This is the first case of adult retinoblastoma to be confirmed immuno cytochemically. The tumor was unusual because the differentiated regio ns contained bacillettes composed mostly of blue cones. It is possible that this and other adult retinoblastomas may arise from previously e xisting retinocytomas.