Immunohistochemical expression of CYP11A1, CYP11B, CYP17, and HSD3B2 in functional and nonfunctional canine adrenocortical tumors

Abstract Background Functionality of human adrenal tumors is inferred by CYP11B1 (cortisol synthase) expression, CYP11B2 (aldosterone synthase) expression, or both. Hypothesis/Objectives Nonfunctional canine adrenal tumors have low expression of steroidogenic enzymes, whereas aldosterone‐producing tumors express CYP11B, and cortisol‐producing tumors express both CYP11B and CYP17. Animals Twenty‐two client‐owned dogs with adrenocortical tumors (ACT) (8 nonfunctional, 7‐cortisol producing, 2 aldosterone‐producing and 5 functional noncortisol producing) and 2 dogs with normal adrenal glands. Methods Retrospective case series. Adrenal functionality was determined from clinical signs and endocrine testing. CYP11A1, CYP11B, CYP17, and HSD3B2 expression was detected by immunohistochemistry on formalin‐fixed paraffin‐embedded adrenal tissue. Protein expression was semiquantified by 2 blinded observers using H‐scoring (results reported as median [range]) and compared in nonfunctional and cortisol‐producing adrenal tumors by Mann‐Whitney U tests. Results CYP11A1, CYP11B, and HSD3B2 were present within all cortical layers of normal adrenal glands, and CYP17 was expressed within the zona fasciculata and zona reticularis. Expression of CYP11A1 (191.25 [97.5‐270] vs. 175 [102.5‐295] P = .69), CYP11B (190 [130‐265] vs. 147.5 [95‐202.5]; P = .07), CYP17 (177.5 [87.5‐240] vs. 247.5 [55‐292.5]; P = .40), and HSD3B2 (230 [47.5‐295] vs. 277.5 [67.5‐295]; P = .34) were not significantly different between cortisol‐producing and nonfunctional ACT. Conclusions and Clinical Importance Our findings suggest it is not possible to determine functionality of canine ACT by immunohistochemistry for steroidogenic enzymes. Tumor size cannot be used to infer functionality of adrenal tumors.