Figure 8b. Osteosarcoma after bilateral retinoblastoma in a 13-year-old girl who presented with a nasopharyngeal mass. The patient had undergone treatment for bilateral retinoblastoma at a young age. (a) CT scan shows a heterogeneous mass with areas of iso- and hypoattenuation that involves the maxillary antrum on the right side. Associated osseous destruction of the posterior maxillary sinus wall and nasopharyngeal protrusion are also seen (arrows). (b, c) Axial fat-saturated T2-weighted (b) and coronal contrast-enhanced fat-saturated T1-weighted (c) MR images demonstrate an extensive soft-tissue mass that arises from the right maxilla. Biopsy revealed undifferentiated osteosarcoma. Chemotherapy and surgery produced very good results, although the follow-up period has been very short.