Cavitary retinoblastoma with MYCN amplification.

MYCN amplification within the tumor has emerged as an important factor in the oncogenesis of a subset of retinoblastomas, most of which are caused by pathogenic variants in the RB1 gene. We present the case of a 3-month-old girl with unilateral cavitary retinoblastoma that initially responded well to intra-arterial chemotherapy but later recurred. After enucleation, the tumor was found to exhibit MYCN amplification, but there were no RB1 variants. Retinoblastoma tumors with MYCN amplification are known to carry a poor prognosis and often require enucleation. On the contrary, cavitary retinoblastomas tend to be well differentiated, with favorable prognosis. To our knowledge, this is the first report of a MYCN-amplified tumor presenting as cavitary retinoblastoma.