Biochemical and ultrastructural features of human milk and nipple aspiratefluids

Breast duct epithelium produces, secretes, and metabolises several biologic ally important compounds, which are found in breast secretions obtained in physiologic and pathologic conditions (milk and nipple aspirate fluids, res pectively). In order to preliminarily evaluate the ultrastructural morpholo gy of the cells found in Type II nipple aspirate fluids (NAF) and correlate it with the biochemical profile of the extracellular fluid present in thes e breast secretions and in human milk, we analyzed 72 NAFs from nonlactatin g premenopausal women affected by various breast diseases and 10 normal mil k samples. Although several constitutive proteins were detected in all samp les examined, the preliminary biochemical analyses and electrophoretic prof iles revealed characteristic behaviours for several biologic constituents, suggesting a possible basic mechanism of production by breast epithelial ce lls during both physiologic and pathologic conditions. The ultrastructural analysis of milk cellular components give preliminary evidence of the apocr ine secretion mechanism peculiar of breast gland, whereas Type II NAF cells appeared as biosynthetically active cells, showing a possible modified sec retion mechanism. Our multidisciplinary approach seems to support the hypot hesis that cellular and biochemical behaviour of Type II NAF may be an usef ul tool to identify aberrated breast epithelial cells in nonlactating women that might be prone to premalignant transformation. J. Clin. Lab. Anal. 14 :330-335, 2000. (C) 2000 Wiley-Liss, Inc.