MALIGNANCY AFTER RETINOBLASTOMA - SECONDARY-CANCER OR RECURRENCE

The risk of second malignancy after retinoblastoma is reported to be a s high as 20% at 10 years after initial diagnosis. This incidence may be an overestimate because of difficulties in distinguishing a second malignancy from recurrent tumor. We encountered a patient with bilater al retinoblastoma who developed a temporal mass 3.5 years after initia l treatment for what had first been diagnosed as rhabdomyosarcoma; fur ther study suggested that it was recurrent retinoblastoma manifesting as primitive neuroectodermal tumor (PNET) with multilineage differenti ation. Chromosome 13 abnormalities were compatible with either rhabdom yosarcoma or recurrent retinoblastoma. To determine how often second m alignancies in retinoblastoma patients may be confused with recurrent primary tumor, we reviewed our experience at Children's Hospital of Pi ttsburgh. Of 43 retinoblastoma patients seen between 1951 and 1992, pr esumed second malignancies were documented in four, including the curr ent case. Of the three other second tumors, one had both neural and sk eletal muscle differentiation; another was diagnosed as rhabdomyosarco ma unclassifiable as embryonal or alveolar; the last was an osteosarco ma. Only the osteosarcoma was clearly a second neoplasm; two and perha ps three of the other cases may be recurrent retinoblastoma. The disti nction between second malignancy and recurrent retinoblastoma may be d ifficult but is worth determining, because treatment may differ, depen ding on the correct designation. Copyright (C) 1997 by W.B. Saunders C ompany.