Abstract
Retinoblastoma(RB) patients have a high risk to develop second malignant
neoplasm (SMN). Diencephalic tumors(DT) are rare in paediatric age. A
retrospective review was performed over 21 years period. Out of 169 RB
patients, 3 presented a DT. Two patients presented a Rb1 germline
mutation and none received radiotherapy. DT in previously treated RB
patients seems a peculiar SMN. However, considering the site, the short
time interval from RB and the absence of radiotherapy, an alternative
pathogenic mechanism could be supposed. The same embryological origin of
the retina and the diencephalon should be considered and biological
studies are needed.