In addition to KCa3.1, we identified also the distantly related, voltage- and Ca2+-activated KCa1.1 channel as a differentially expressed channel in the two tumor types (3-fold higher mRNA expression and presence of functional KCa1.1 currents in ccRCC but not in oncocytoma) and between healthy and tumor tissue of the same kidney. Here, KCNMA1 is linked to oncocytic adenoma.