We determined the biochemical composition of fluid aspirated from 52
breast cysts and classified the
cysts into types I and II on the basis of the
potassium-to-
sodium (K/Na) ratio in the fluid. In this study, we confirmed the presence of
prostate-specific antigen (PSA) in some
breast cyst fluids, regardless of whether
cysts were type 1 or type 2, or benign or malignant. On immunohistochemical study, we found no direct correlation between the presence of PSA and
progesterone receptors, which is at odds with the results of earlier reports. Current practice in cytologic study appears to favor the examination of bloody fluid. In this study, two samples found to contain malignant cells were cloudy or turbid. We therefore recommend that all cloudy or turbid cyst fluids should be subjected to cytologic examination. This study indicated that the
potassium and
sodium concentrations were not the same in multiple
cysts in the same individuals. In addition, apocrine cells were observed in both type 1 and type 2
cysts. Therefore,
breast cyst type cannot predict the natural history of cystic changes or indicate the likelihood of
cancer. The finding of
malignancy in two patients with type 2
cysts also supports this argument.