Abstract Introduction Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia is a rare pulmonary disorder that manifests with a diffuse proliferation of pulmonary neuroendocrine cells in the airway epithelium. It is a precursor lesion to pulmonary carcinoid tumors and is most diagnosed in nonsmoking, middle-aged females. Its occurrence in a male smoker with emphysema is rare and expands the clinical spectrum of this underrecognized disease. Case Presentation A 72-year-old man with a history of severe centrilobular emphysema and a 57-pack-year smoking history was being followed for several bilateral pulmonary nodules that had been increasing in size over several years. His dominant right lower lobe lesion measured 1 cm and demonstrated mild metabolic uptake on PET (SUV 2.1). He endorsed an intermittent cough and wheezing but denied hemoptysis, fever, or weight loss. After referral to a multidisciplinary thoracic tumor board for discussion of the progressive radiographic findings and indeterminate PET activity, a robotic-assisted bronchoscopy was recommended for tissue diagnosis and was successfully performed.Histopathology revealed small groups of epithelioid cells with elongated nuclei in endobronchial and alveolar spaces without necrosis, mitotic figures, or significant atypia (Fig. 1). Immunohistochemistry (IHC) demonstrated diffuse strong positivity for synaptophysin and INSM1, focal positivity for TTF-1, weak cytokeratin (AE1/AE3) expression, and negativity for EMA and CD56. The Ki-67 index was 2%. The overall histopathologic and IHC findings were consistent with a low-grade neuroendocrine proliferation, and a diagnosis of DIPNECH was established.DIPNECH was diagnosed in a male smoker with emphysema, a clinical presentation that is exceedingly rare. The patient continued on inhaled therapy, counseled to quit smoking, and placed on surveillance CT scans every 6 months. Discussion DIPNECH is a rare pulmonary disorder typically affecting middle-aged, nonsmoking women; reports in men or smokers are exceptional. This case illustrates the importance of considering DIPNECH in atypical populations and demonstrates the utility of a multidisciplinary approach and tissue diagnosis in indeterminate pulmonary nodules. The coexistence of emphysema and neuroendocrine proliferation suggests that chronic airway injury may contribute to disease pathogenesis rather than DIPNECH being purely idiopathic. A few reports describe such an overlap. Recognition in this atypical setting prevents misdiagnosis as metastatic disease or COPD-related nodularity. Conclusion This case underscores the need for refined diagnostic criteria and inclusion of nontraditional populations in future research, reinforcing that DIPNECH can occur beyond its classic demographic and may represent an underdiagnosed entity in smokers with multifocal nodules. References: Available upon request or will be included in poster This abstract is funded by: None
Karishma et al. (Fri,) studied this question.