Newly Identified Gross Human Anatomy: Eight Paired Vestigial Breast Mounds Run along the Embryological Mammary Ridges in Lean Adults

Although isolated accessory breasts have been reported in many locations on the torso, we noted that lean men presenting for liposuction had mounds of fullness in a curvilinear array (axilla to groin) consistent with the configuration of the embryological mammary ridge. We hypothesized that grid mapping and pinch testing would elucidate the pattern of fullness and its relation to the "milk line." Twenty lean participants (10 men, 10 women) each underwent standardized photography and grid mapping of anterior torsos. We then pinch-tested each for subcutaneous fullness in 250 standardized loci. We used plotted pinch values and OLS regression models to determine if focal fullness corresponded to published configurations of the embryologic mammary ridge. We identified a pattern of paired mounds in all participants running bilaterally in curved linear arrays from axillae to groin in the exact form of milk lines. Regression models applied to the male and female pinch data indicated that focal thickness matched mammary ridge configurations in all subjects ( = 0.023 for men,