Supplementary Material for: Diffuse Idiopathic Pulmonary Neuroendocrine Cell Hyperplasia: A Blanked Out Pulmonary Neuroendocrine Tumor

Introduction: Lung neuroendocrine tumors (NETs) are a rare type of pulmonary tumor and represent approximately 2% of all lung cancers. The prevalence of lung NETs is increasing, which may be due to improved diagnostic techniques for asymptomatic tumors. Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) is a rare and underdiagnosed disease that falls under the spectrum of neuroendocrine tumors. Case Presentation: We presented a case of a 59-year-old male who presented with severe coughing spells, flushing, and diarrhea. His CT scan showed innumerable pulmonary nodules and irregular nodular opacities throughout the lungs. He underwent a left upper lobe wedge resection and was eventually diagnosed with neuroendocrine tumorlets via immunohistochemical stains. He was started on a trial of octreotide and reported significant improvement in symptoms after one month. Conclusion: DIPNECH is a rare pre-invasive lesion characterized by the abnormal proliferation of pulmonary neuroendocrine cells. Patients with DIPNECH can present initially with respiratory symptoms, while other cases are discovered incidentally during the workup of different conditions. Definitive diagnosis of DIPNECH requires histopathological examination of lung tissue. There is limited evidence on DIPNECH management, and an individualized approach is currently advised.