Multifocal osteosarcoma as second tumor after childhood retinoblastoma

We present a case of multifocal osteosarcoma (MFOS) arising 11.5 years afte r successful treatment of bilateral retinoblastoma. The clinical, imaging a nd pathological findings at onset, after therapy, and during follow-up are described. Fluorescent in situ hybridization did not reveal a deletion of t he RB-1 retinoblastoma gene, although the presence of an inactivating mutat ion invisible to this method cannot be ruled out. The MFOS may have been a second multifocal tumor associated with the original retinoblastoma or a po st-irradiation sarcoma with extensive metastases.