Should I estimate age at last follow up and year of birth if they are missing?

Yes, certainly in cases where the person is known to have developed cancer. For example, consider a pedigree where the consultand is 30 years of age in 2007, and the consultand’s grandmother died of ovarian cancer at age 40, but there are no details of the grandmother’s year of birth. In this case, we should make some estimate of the grandmother’s year of birth (e.g. 2007 – 30 – 25 – 25 = 1927) and include this information in the input pedigree. Otherwise, mutation carrier probabilities and cancer risks will be underestimated.