The two more prominent types were breast and colon cancer. Even though medical community considers a patients with family history of breast or colon cancer high risk, there is a common tendency to not focus too much on hereditary aspect. While this may have opened new avenues of research, this has also stifled the research in the field of cancer genetics as Lynch felt back in 1960s. "Henry T. Lynch thought that he had discovered the existence of hereditary cancers among Nebraskan families in the 1960s, his hope was that it would lead to more effective means of cancer control. Lynch argued that the identification of such cancers offered tremendous opportunities for improving detection and treatment. If cancer ran in families, he claimed, the discovery of a hereditary cancer in one family member should be an alert to the possibility of cancer in others, and so prompt careful scrutiny for any signs that might indicate the presence of the disease in "healthy" individuals. However, in the 1960s and 1970s & #8230;cancer experts doubted his claim to have identified hereditary cancers, and ACS education efforts routinely stated that cancer was not a hereditary disease. Thus, Lynch's scheme for improving cancer detection and treatment seemed to falter almost before it began." (Cantor, 2006)

Following Lynch's research however, more people entered the field and began investigating the connection between cancer and heredity. Knudson in his research found that gene mutation plays a key role. He found that while people with positive family history are at a great risk of developing some types of cancers, almost equal number of people with apparent lack of family history of cancer can develop the same type. He consulted many researches and discovered that the reason behind this was bilaterally affected parents. The children of such parents were equally at risk even if there was no family history of cancer. However children of unilaterally affected parents with no family history had a very low risk of developing certain type of cancer. He also then explained how gene mutation differed in hereditary and non-hereditary types of cancer.

Discussing the case of retinoblastoma, Knudson explained that this is one type of cancer which has often been connected with genes. But...

This meant that there was a subgroup that accounted for the other cases of retinoblastoma. And that could also explain why some children will develop cancer and others won't even with affected parents. He thus found that: "the offspring of bilaterally affected survivors with no previous family history of the tumor do have a very nearly 50T probability of being affected, just as with individuals with a positive family history, whereas the offspring of unilaterally affected individuals with a negative family history have only a 10 to 15% risk. Yet when offspring are affected, the fraction with bilateral tumor is high (60 to 70%), whether the parent had unilateral or bilateral disease." (p. 77-78)
With the discovery of DNA patterns and human genome, more research is likely in the field of cancer genetics soon. This will help clear the confusion but from the research so far, it has been found that cancer is not caused by heredity alone in most cases. There may be some other factors at play affecting the patient's chances of developing cancer. These factors are mostly environmental and in some cases certain gene mutation may also determine while some carriers develop cancer and others don't. Still till further research gives us any conclusive results, it is safer for people with positive cancer history to go for regular screening and take extra care of their health. Women with a family history of breast cancer are thus advised to regularly go for mammography to be able to nip the problem in its early stages. This however doesn't rule out the fact that many women with no family history will still develop breast cancer and many with positive history will completely escape the danger. This confusion can only be cleared with the help of new and more extensive research.