Scanning electron microscopy of retinoblastoma.

Two cases of the so-called undifferentiated retinoblastoma are demonstrated where typical rosettes were absent. However, cell groups resembling rosettes existed. Scanning electron microscopy revealed a tendency of the cells to arrange in circles or in garland-like formations. In one of the cases lymphocytes were found and in the other photoreceptor elements and tubuloreticular inclusions within the endothelial cells were seen.