Is retinoblastoma inherited ?
Researchers estimate that 40 percent of all retinoblastomas are germinal, which means that RB1 mutations occur in all of the body's cells, including reproductive cells (sperm or eggs). People with germinal retinoblastoma may have a family history of the disease, and they are at risk of passing on the mutated RB1 gene to the next generation. The other 60 percent of retinoblastomas are non-germinal, which means that RB1 mutations occur only in the eye and cannot be passed to the next generation.  In germinal retinoblastoma, mutations in the RB1 gene appear to be inherited in an autosomal dominant pattern. Autosomal dominant inheritance suggests that one copy of the altered gene in each cell is sufficient to increase cancer risk. A person with germinal retinoblastoma may inherit an altered copy of the gene from one parent, or the altered gene may be the result of a new mutation that occurs in an egg or sperm cell or just after fertilization. For retinoblastoma to develop, a mutation involving the other copy of the RB1 gene must occur in retinal cells during the person's lifetime. This second mutation usually occurs in childhood, typically leading to the development of retinoblastoma in both eyes.  In the non-germinal form of retinoblastoma, typically only one eye is affected and there is no family history of the disease. Affected individuals are born with two normal copies of the RB1 gene. Then, usually in early childhood, both copies of the RB1 gene in retinal cells acquire mutations or are lost. People with non-germinal retinoblastoma are not at risk of passing these RB1 mutations to their children. However, without genetic testing it can be difficult to tell whether a person with retinoblastoma in one eye has the germinal or the non-germinal form of the disease.