Mengoli M, et al. - Authors pursued a comparison of the clinical, radiologic, histologic, immunohistochemical, and molecular features of diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) and isolated carcinoids with/without neuroendocrine cell hyperplasia (NECH). Among immunohistochemical markers, DIPNECH correlated with higher expression of thyroid transcription factor-1, CD10, and gastrin-releasing peptide/bombesin-like peptide. Nonetheless, when a purely histopathologic definition of DIPNECH was applied, diagnostic criteria for DIPNECH was met by 40% of isolated carcinoids, even in the absence of symptoms and/or radiologic abnormalities. Since DIPNECH depicted a distinct clinical syndrome, the term DIPNECH appeared to be limited to cases presenting with respiratory symptoms, functional and/or radiologic abnormalities and constrictive bronchiolitis on histology.