Recent evidence suggests that the heterogeneous cytomorphological features of an aldosterone-producing adenoma may be related to its underlying genotype, reflecting different CYP11B2 (aldosterone synthase) and CYP11B1 (11β-hydroxylase that converts 11-deoxycortisol to cortisol) expression profile in the tumor (see below) (14–18). This evidence concerns the gene CYP11B1 and neoplasm.