Adrenocorticotropic Hormone-Independent Bilateral Adrenocortical Macronodular Hyperplasia: A Case Report and Immunohistochemical Studies

A 55-year-old woman developed Cushing's syndrome due to ACTH-independent bilateral adrenocortical macronodular hyperplasia. Plasma ACTH was undetectable, and was not stimulated by administration of metyrapone, CRH, or insulin. Hypercortisolism was not suppressed by a high dose of dexamethasone, but was responsive to ACTH. Both adrenal glands were enlarged with a total weight of 200g, and contained multiple nodules composed of two cell types (large clear cells and small compact cells). In immunohistochemical studies, P450c17 immunoreactivity was predominantly observed in small compact cortical cells, while that of 3βHSD was observed exclusively in large clear cortical cells. This pattern of expression of steroidogenic enzymes as well as histological and clinical features is considered to be unique to ACTH-independent bilateral adrenocortical macronodular hyperplasia.