Primary pigmented nodular adrenocortical disease (PPNAD): immunohistochemical and in situ hybridization analysis of steroidogenic enzymes in eight cases.

Primary pigmented nodular adrenocortical disease (PPNAD) is a rare but an interesting adrenocortical disorder associated with ACTH-independent hypercortisolism. We have studied eight cases of the adrenals with PPNAD by immunohistochemistry of all steroidogenic enzymes involved in cortisol biosynthesis (P-45scc, 3 beta-HSD, P-450c21, P-45017 alpha, and P-45011 beta) and also by performing in situ hybridization of P-45017 alpha in seven cases in order to localize the sites of specific steroidogenesis in this unique disorder. Immunoreactivity of all the enzymes examined was intense in almost all of the cells in adrenocortical nodules, especially the cells with abundant eosinophilic cytoplasm in all the cases examined. The internodular cortex, which demonstrated atrophy in five cases, normal appearance in two cases and hyperplasia in one case, was negative for the enzymes with an exception of 3 beta-HSD. Hybridization signals of P-45017 alpha were condensed over the nodules in in situ hybridization study, suggestive of an increased production of the enzyme itself in cortical cells of the nodules. These results may be consistent with autonomous cortisol production by the nodular cells and indicate that almost all of the cells in the nodules produce cortisol, which can also explain the presence of hypercortisolism despite small sizes of adrenals in PPNAD. Immunoreactivity of steroidogenic enzymes is observed in a small cluster of cortical cells with abundant eosinophilic cytoplasm located at the zona reticularis but not in adjacent non-nodular cortex, which may support an abnormal development of the zona reticularis as a possible pathogenesis of this disorder.