Cationic content in multiple mammary cysts.

One hundred and ninety-six breast cyst fluid samples from 78 consecutive patients with multiple cysts were subdivided according to the K+/Na+ ratio: type 1 (K+/Na+ ratio > 1) and type 2 (K+/Na+ ratio < or = 1). Cysts of the same type were found in 57.7% of patients (concordant group). Such a finding suggests that in patients bearing multiple cysts, all aspirated fluids need to be classified on the basis of their cationic composition. In the concordant group, type 1 cysts were more frequent than in the discordant group (80.3% vs 59.5%, P = 0.002). High K+/Na+ ratios (> 4.0) were present in 64% of type 1 cysts in the concordant group compared to 37.7% in the discordant group (P = 0.001), which suggests a different activity of the epithelium lining the cyst wall.