Endocrine Abstracts

Introduction: Primary aldosteronism (PA) is an important cause of hypertension. Adrenal hyperplasia (AH) and aldosterone-producing adrenocortical adenoma (APA) are considered the most frequent causes of PA. Histopathological analysis of unilateral PA has been difficult since no clear morphological criteria existed for defining aldosterone-producing cells. Recently, the distribution of adrenal cells forming aldosterone and cortisol has been studied by using specific monoclonal antibodies against the enzymes CYP11B2 and CYP11B1, catabolizing the final steps of aldosterone and cortisol production, respectively. In addition to APA and AH, the antibodies allow identification of unilateral multiple micronodules (UMN), expressing CYP11B2 in the zona glomerulosa (ZG), and aldosterone-producing cell clusters (APCC) extending beyond the ZG. The aim of this study was to review the histopathological diagnoses of all patients who underwent adrenalectomy for unilateral PA in Iceland in 2007–2016, using immunohistochemical staining.

Methods: Tissue slides from all patients, aged ≥18 years, who underwent adrenalectomy for unilateral PA in Landspitali University Hospital (LUH) in 2007–2016, were accessed and appropriate slides from each patient selected. Antibodies; anti-CYP11B1 (clone 80-7 Mabs 502, rat), and anti-CYP11B2 (clone 41-17B Mabs 1251, mouse), were purchased from Merck Millipore and diluted 1 : 200 using EnVision Flex Antibody Diluent (DM830, Daco). The PA tissue slides were stained along with control samples from healthy adrenal glands using AutostainerLink 48 (Daco). Microscopic evaluation was thereafter performed. All necessary permissions were obtained.

Results: In 2007–2016, a total of 25 patients underwent adrenalectomy as treatment for unilateral PA in LUH. Twenty of them had originally been diagnosed with APA, four with AH and one as inconclusive. After performing the immunohistochemical staining, 7 of the 25 patients’ (28%) histopathological diagnoses were changed. In total, 20 of the 25 patients (80%) had APA, three (12%) had APCC and two (8%) had UMN. Out of four patients previously diagnosed with AH, two had APA, one had APCC and one had UMN. One patient previously diagnosed with APA turned out to have APCC and another one UMN. The inconclusive sample proved to contain APCC.

Conclusions: Most of the patients turned out to have APA, with APCC being the second most prevalent histopathological diagnosis. Interestingly, no-one had AH. These findings emphasize the importance of the immunohistochemical staining for the proper histopathological diagnosis of PA patients. Further research is needed regarding APCC and UMN. Moreover, it is important to make further assessment on treatment response in context with precise histopathological diagnosis.