Genetic diagnosis of retinoblastoma by a combination of fluorescence in situ hybridization and restriction fragment length polymorphism

PURPOSE: It is important to exclude germ line mutation in cases of unilateral retinoblastoma(RB) to estimate hereditary or possible secondary cancer. We investigated whether genetic diagnosis is feasible in a health check screening program. METHODS: Five patients with RB had surgery for enucleation in Keio University Hospital. Tumor cells from enucleated eyes and lymphocytes representing systemic cells were collected and analyzed genetically by fluorescence in situ hybridization(FISH) and restriction fragment length polymorphism (RFLP). RESULTS: One out of three unilateral RB cases could be diagnosed as non-hereditary by the finding of no copies of the RB gene in the tumor cells using the FISH method and no signal in the RFLP method. A decrease of signal in tumor cells to less than 50% in the RFLP method was observed in another case of unilateral RB that seemed to be non-hereditary, but the case ultimately could not be diagnosed as non-hereditary because polycopies were found in the FISH method. No abnormality in tumor cells could be found in another unilateral case or in systemic cells of two bilateral cases. CONCLUSION: A combination of FISH and RFLP methods can be used to diagnose some cases of RB as non-hereditary.