PRECLINICAL STUDY Breast duct anatomy in the human nipple: three-dimensional patterns and clinical implications

Background The anatomy of the nipple has become clinically relevant. Diagnostic techniques access the breast through nipple ducts and surgeons offer nipplesparing mastectomy. There is variation in the number of ducts reported and little is known about the spatial location of ducts, their size, and their relationship to orifices on the surface. Methods Nipple specimens were taken from 129 consecutive mastectomies. Each was sectioned coronally into 3 mm blocks and one section was prepared from each block. The number of ducts and cross-sectional areas of nipple and duct ‘bundle’ were recorded. Three nipples were sectioned at 50 lm intervals and digitally reconstructed in three dimensions. Results The median number of ducts was 23 (interquartile range 19–28). Reconstructions and summary data from 25 nipples show a central duct bundle narrowing to form a ‘waist’ as the ducts enter breast parenchyma. A three-dimensional reconstruction focusing on one nipple tip demonstrated 29 ducts arising from 15 orifices. Beneath the skin, most ducts are very narrow, gradually becoming larger deeper within the nipple. Conclusions This work demonstrates that many ducts share a few common openings onto the surface of the nipple, explaining the observed discrepancy between number of ducts and of orifices. Neither duct diameter nor position predicts whether a duct system will terminate close to the nipple or pass deeper into the breast. These new insights into nipple anatomy will be of use in considering the reliability of a ductal approach to diagnosis and in planning nipple-sparing mastectomy.