Second malignant neoplasms in retinoblastoma. Fact and fiction

Second malignant neoplasms (SMN) are distinct from primary neoplasms in site, time and histology. SMN may arise by chance or due to the influences of chemotherapeutic agents, therapeutic irradiation or genetic predisposition. Patients with the hereditary form of retinoblastoma (RB) appear genetically predisposed to the development of connective tissue tumours, particularly osteosarcoma. Therapeutic irradiation is an additional risk. Quantitation of the risk of SMN in RB patients may be influenced by selection biases and inappropriate analyses. Much of the biases in reported series arises from the limitations of single-centre studies. Loss of patients to follow-up, failure to adhere to properly defined criteria of SMN and to consider the risk of malignancy in the general population may have led to over-estimation of the risk of SMN in retinoblastoma patients.