Incidental neuroblastoma with bilateral retinoblastoma: what are the chances?

A child with bilateral familial retinoblastoma underwent staging MRI brain and orbit which identified subtle leptomeningeal enhancement, thus prompting an MRI whole body, which revealed a retroperitoneal mass, confirmed on laparoscopic biopsy to be neuroblastoma. This is the first reported case of these two rare embryonal non-central nervous system tumors occurring concurrently. The cause of this concurrence is unknown despite their pathogenic similarities with a chance of 4 cases per 10 billion children aged 1-4 years. Incidental neuroblastomas in infants can regress spontaneously but this child underwent systemic chemotherapy for his retinoblastoma that may have caused regression of the neuroblastoma.