• Question: What are the chances of identical twins getting the exact same cancer in the same place?

    Asked by bechope to Leo, Jo, Iain on 24 Jun 2010 in Categories: .
    • Photo: Leo Garcia

      Leo Garcia answered on 24 Jun 2010:

      Interesting idea… Specific kinds of cancer are known to occur in families:


      And considering that some cancers are heritable (that is, due to genes you inherit from your parents), it would be logical to assume that twins (who have the same genes) would get the same cancer, also considering that their environmental conditions are almost the same (at least for the first part of their lives).

      Analysing cancer in twins in hard, because twins are relatively rare:


      I think the chances of them getting the exact same cancer in the same place is very rare – although one twin having a one kind of cancer is linked to a high probability of the other getting it, depending on the kind of cancer. Here:


      also says that there is only an increased risk of so-called ‘familial’ (that is, inherited) breast cancers occurring in both twins. I think stories like this:


      Where twins have got both developed the same kind of cancer in a reasonably short space of time, are the exception, rather than the rule. There are so many other factors OTHER than genetic which can trigger cancer (although it is important not to downplay the role of genetics), that the kind of situation you describe would be exceedingly rare, and possibly just coincidental.