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.
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.
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.