RB1 and retinoblastoma: Retinocytoma could also be a manifestation of low‐penetrance retinoblastoma (Dryja, Rapaport, McGee, Nork, & Schwartz, 1993; Harbour, 2001; Kratzke et al., 1994).It is possible that proteins encoded by RB1 gene variants retain part of the wild‐type protein function (Lohmann, Brandt, Hopping, Passarge, & Horsthemke, 1994).