Clinical studies dating back decades report a disproportionately high number of female breast cancers originating in the upper outer quadrant of the breast [1], and although this is attributed to a greater amount of epithelial tissue in that region, it is also the area to which underarm cosmetic products are applied [2, 3]. Early studies reported 31% of cancers in the upper outer quadrant [1], but later studies in the 1990s report up to 61% [2, 3]. The annually recorded quadrant incidence of breast cancer in Britain documents a rise in England and Wales from 47.9% in the upper outer quadrant in 1979 to 53.3% in 2000, and in Scotland a rise from 38.3% in the upper outer quadrant in 1980 to 54.7% in 2001 [4]. Any increase in the disproportionality of breast cancer in the upper outer quadrant would be inconsistent with an explanation relating to the greater amount of target epithelial tissue in that region but does parallel the increasing use of cosmetics in the underarm area [2, 3, 4, 5].
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