Dear Pattyp, I have not heard nor could I find anything particular to occurance of breast masses, increased incidence of left vs. right. In the sources I looked under there was no mention of that, particularly in relation to breast cancer. I'm not even sure where you would look for that information. Perhaps in a surgical textbook?
My doctor told me it does occur more in the left breast.
I have a theary on this. I believe the statistics show more cancer in the left breast than the right breast. My theary is that that is because more people are right handed and therefore use their left side of the body for more abusive things. Mothers who are right handed hole their babies in their left arms while trying to do other things. The left side gets more abuse that way. Its just my theary, but I think if a study was done it would show this.