Lactate dehydrogenase, isoenzyme patterns and cation levels in human breast gross cyst fluid

In order to investigate the diagnostic and/or prognostic value of total activity and isoenzymatic patterns of lactate dehydrogenase, 24 human breast gross cystic fluids were studied. A comparison of total lactate dehydrogenase activity to the serum level revealed an increased activity in about 63% of the cases examined; moreover, a significant increase in the slow-moving lactate dehydrogenase 4 and 5 isoenzymes was observed in some cyst fluids. The levels of Na+ and K+ concentrations were also analyzed and two classes of cysts were identified: one presenting Na+ and K+ levels similar to those found in extracellular compartment; the other with high K+ and low Na+ levels, characteristic of an intracellular fluid. This latter pattern could indicate an active metabolism of the epithelial cells lining the cysts. This breast cyst fluid also showed increased levels of lactate dehydrogenase 4 and 5 isoenzymes. The correlation between an increased activity of lactate dehydrogenase 4 and 5 isoenzymes and high K+ and low Na+ levels could be the expression of a high biosynthetic activity and of an anaerobic metabolism in some cysts, suggesting the evolution of the breast gross cyst lesion to malignancy. The importance of these observations is discussed.