Abstract 008: Novel Pathological Diagnosis Between Aldosterone Producing Adenoma And Idiopathic Hyperaldosteronism

The expressions of steroidogenic enzymes to produce aldosterone like CYP11B1, CYP11B2, 3BHSD1 and 3BHSD2 remain to be clarified to confirm pathological subclassification between aldosterone-producing adenoma (APA) and idiopathic hyperaldosteronism (IHA). Furthermore, we examined the correlation between APA tumor size and the status of intratumoral steroidogenic enzymes involved in aldosterone biosynthesis using immunohistochemistry. Surgically proven forty APA patients and ten IHA patients were retrospectively studied. Multi-detector computed tomography, AVS, and laparoscopic adrenalectomy were performed in all of the patients studied. The tumor area of APA at the maximum diameter of the sections was precisely measured by ImageJ software. The status of steroidogenic enzymes was immunohistochemically analyzed using monoclonal antibodies for CYP11B1, CYP11B2, 3BHSD1 and 3BHSD2, and the findings were evaluated according to the H-score system, based on both the number of immunopositive cells and relative immunointensity. Adrenal masses were not detected by computed tomography in 20 APA patients.In all of 10 IHA patients, hyperplastic zona glomerulosa was accompanied by an expression of HSD3B1. In contrast, tumor cells in all 40 APA patients were not immunopositive to HSD3B1, but strongly and dominanty expressed HSD3B2. Perhaps, due to compensatory responses to excess aldosterone, APA had an adjacent zona glomerulosa whose immunoreactivities to HSD3B1 and HSD3B2 were profoundly reduced in all 40 APA patients. Maximum tumor area obtained in the specimens was significantly correlated with preoperative plasma aldosterone concentration, urinary aldosterone excretion, the H-score of CYP11B1, and was inversely correlated with the H-score of CYP11B2. These results demonstrated that small adenomas could produce sufficient aldosterone to cause clinically overt primary aldosteronism because of the significantly higher CYP11B2 expression per tumor area. Monoclonal antibodies against HSD3B1 and HSD3B2 could be useful for immunohistochemical differentiation between APA and IHA. In addition, the relatively higher CYP11B2 expression per area in smaller APA could clinically cause PA despite their CT-undetectable tumor size.