Second primary osteosarcoma with rosette-like structure in a patient with retinoblastoma.

A Japanese male patient developed bilateral retinoblastomas at the age of 1 year, but remained continuously disease-free after enucleation of the left eye and radiation therapy to the right eye. He noticed a painless hard mass around the right temporal bone when he was 25 years old. Biopsy specimen showed a small multi-nodular proliferation of tumor cells with prominent rosette-like structures. Eosinophilic material with focal mineralization was seen in the center of the rosettes. Immunostaining of the tumor cells showed positive reactions for epithelial membrane antigens CD 56 and CD 99. The patient was treated with systemic chemotherapy, and the tumor partially diminished. It is well known that a few osteosarcomas show a rosette-like appearance with production of osteoid in the center, but this is the first case of second primary osteosarcoma with prominent rosette-like features.