I am getting, in my opinion, very conflicting information from sources about the inheritance of retinoblastoma, a type of cancer. Hereditary retinoblastoma is associated with defects in the gene encoding the cell cycle-regulating, tumor suppressor protein RB1. Most sites claim that retinoblastoma is inherited in an autosomal dominant manner, which would suggest that the offspring only need one defective allele to inherit the condition. At the same time, however, all online sources claim that only one working copy of a tumor suppressor gene is required to maintain its functionality and that both copies of a tumor suppressor gene must be defective for the onset of cancer. This understanding is known as the two-hit hypothesis. But to me, this idea clearly conflicts the claim that retinoblastoma is an autosomal dominant condition and suggests the opposite: that, in order to develop retinoblastoma, there can be no working copies of the RB1 (tumor-suppressing) gene (hence making retinoblastoma an autosomal recessive disorder).
I don't know if there are any flaws in my interpretation and if somehow both explanations are correct with the issue being me not understanding it clearly. How can a condition be autosomal dominant (i.e. requiring only one affected allele) while also only requiring one working allele to prevent it? It seems illogical.