The article Fish is Positively Associated with Breast Cancer Incidence Rate may be a little difficult to understand (except for the title and the last sentence, both of which are pretty clear). Fortunately, the full text of the study has been summarized in simple language by Dr. Michael Greger, a physician who specializes in nutrition, essentially as follows:

A. Fish Consumption and Breast Cancer

In general, experiments on nonhuman animals has shown a protective effect of fish consumption on breast cancer risk, which is one of the reasons some authorities recommend that women eat fish. Yet there have never been any large forward-looking human studies. Never, that is, until now.

The results of the Diet Cancer and Health Study were finally published last month in the Journal of Nutrition. Over 20,000 women were grilled about their fish consumption with a detailed questionnaire and then followed for 5 years. And those eating the most fish had a 50% greater risk of developing breast cancer. The researchers estimate that women may raise their breast cancer risk 13% for every 25 grams of fish they eat every day (which is but a quarter of a serving). And the increased breast cancer risk from fish consumption held strong even after controlling for other risk factors such as alcohol and obesity and hormone use, etc.

It didn't matter whether it was fatty fish or lean fish. It didn't matter if the fish was fried, boiled or pickled or smoked or whatever, the more fish these women ate in any form, the more at risk they were for getting breast cancer. Researchers guess it may be the organochlorine pesticides like DDT contaminating the worlds oceans that make fish flesh so carcinogenic.[1]