An analysis of the content and morphology of human breast microcysts

The composition of 40 human breast microcysts, dissected from eight biopsy and 14 mastectomy specimens has been analysed. All contained high concentrations of the androgen conjugate, dehydroepiandrosterone sulphate, the median value being more than 1000 times that of plasma. In ten cysts sufficient fluid was available for cationic analysis and in all the potassium concentration exceeded that of sodium. This composition suggests an apocrine derivation of the constituents of breast microcysts. This is substantiated by the finding of PAS diastase positive granules in the epithelium lining all 40 microcysts. These findings indicate that there is a single population of breast microcysts which are lined by epithelium with apocrine secretory activity.