Subclassification of unilateral primary aldosteronism using an optimal cut-off value for positive CYP11B2 (aldosterone synthase) immunohistochemistry and modified histologic criteria in the Korean population

The histopathology of primary aldosteronism (HISTALDO) consensus indicates the necessity of CYP11B2 (aldosterone synthase) immunostaining in diagnosing primary aldosteronism (PA). However, proper threshold for positive interpretation of CYP11B2 immunostaining is yet to be established. Therefore, we aimed to correlate the subclassification of PA and postsurgical outcomes to define an optimal cut-off value for CYP11B2 immunostaining in 83 unilateral PA patients. Initial 73 classical PA patients using a 1 % cut-off value revealed a similar rate of absence of clinical success between classical PA (9.7 %) and non-classical PA (11.1 %, p > 0.999). The absence of biochemical success was lower in classical PA (4.4 %) than non-classical PA (20.0 %, p = 0.120). After establishing new 30 % cut-off value for CYP11B2 immunostaining, 68 of 83 (81.9 %) patients were re-classified as classical PA. Despite statistical insignificance, the absence of both clinical and biochemical success was lower in classical PA (8.8 % and 4.7 %, respectively) than non-classical PA (14.3 %, p = 0.158; 14.3 %, p = 0.218, respectively). Finally, a modified histologic subclassification was applied according to the presence of single aldosterone producing lesion using both 1 % and 30 % cut-off values. 69 (1 % cut-off) and 64 (30 % cut-off) cases were subclassified as modified classical PA. However, they were not superior to their non-classical counterparts in terms of both clinical and biochemical success using both cut-off values. In summary, the clinical and biochemical outcomes were not successfully predicted by either 1 % or 30 % cut-off values and modified histologic criteria. Further validation study on a larger patient cohort is needed.