Abstract
Although previous studies have described steroidogenic enzyme expression in aldosterone-producing adrenocortical carcinoma (APAC), detailed immunohistochemical evaluations of CYP11B2 at the protein level and its clinicopathological relevance remain limited. Here, we report a rare case of APAC with a comprehensive immunohistochemical analysis focusing on CYP11B2 expression. An 82-year-old woman presented with limb weakness and severe hypokalemia (serum potassium: 1.9 mmol/L). Endocrinological evaluation revealed markedly elevated plasma aldosterone levels and suppressed renin activity, indicating autonomous aldosterone secretion. Imaging identified a rapidly enlarging left adrenal mass with intratumoral hemorrhage, and adrenal venous sampling confirmed unilateral aldosterone excess. The patient underwent laparoscopic left adrenalectomy. Histopathological examination revealed a high-grade adrenocortical carcinoma with positive surgical margins. Immunohistochemical analysis demonstrated positive expression of CYP11B2, CYP11B1, and CYP17A1, whereas dehydroepiandrosterone sulfotransferase expression was absent in the tumor cells but present in the adjacent zona reticularis, suggesting disorganized steroidogenesis. Although biochemical parameters transiently improved postoperatively, the patient developed early recurrence with peritoneal dissemination and died 10 months after surgery. This case of APAC was diagnosed following severe and rapidly progressive hypokalemia, suggesting that a detailed examination of steroidogenic enzyme expression in the tumor may be valuable in elucidating the endocrine characteristics of this rare malignancy.