In the special case of a patient with bilateral ACTH-independent macronodular hyperplasia, diffuse hyperplastic areas and a small nodule showed a polyclonal pattern, whereas a large nodule was monoclonal.
After resection, the nodule proved to be an 8-mm typical pulmonary carcinoid, with positive immunostaining for the classical neuroendocrine markers and for ACTH, and showing tissue expression of the POMC gene.
Additionally, the lungs were suspected as the ACTH source due to high levels of progastrin-releasing peptide and progressive pulmonary consolidation with a contralateral nodule, suggesting SCLC.