Immunodiagnosis of late, recurrent retinoblastoma

The clinical, pathological, and immunohistochemical features of a patient with bilateral retinoblastoma who developed a nasopharyngeal mass seven years following irradiation treatment of the left eye is described. Diagnosis of the new tumor was difficult by routine light microscopy. Immunohistochemical staining of the original globes, the nasopharyngeal mass, and a cervical lymph node biopsy specimen with an antiserum prepared against tissue cultured retinoblastoma cells suggested the diagnosis of metastatic retinoblastoma rather than a "radiation-induced" sarcoma.