Surgically Diagnosed Diffuse Idiopathic Pulmonary Neuroendocrine Cell Hyperplasia in Asymptomatic Patients

Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) is a rare pulmonary precursor lesion that is characterized by the diffuse proliferation of neuroendocrine cells within the airway epithelium. Because obtaining a surgical specimen for histological confirmation is often difficult, management strategies for asymptomatic patients are controversial. It is generally considered an indolent condition that is often managed conservatively. However, diagnosis can be difficult in asymptomatic patients because radiological findings may resemble those of early-stage lung cancer.

We present 2 cases of asymptomatic patients with DIPNECH who were detected incidentally during radiological surveillance. High-resolution CT revealed multiple pulmonary nodules in both patients, accompanied by subtle findings indicative of small-airway involvement, such as mosaic attenuation and air trapping. Despite normal laboratory findings, normal pulmonary function tests, and the absence of respiratory symptoms, serial imaging revealed slow but definite enlargement of a dominant pulmonary nodule, making it difficult to exclude malignancy with confidence. The 1st patient was a 63-year-old nonsmoking woman who was observed for multiple pulmonary nodules over 6 years. During this period, a centrally located dominant nodule in the left lower lobe gradually enlarged, prompting a diagnostic left lower lobectomy. In the 2nd case, a 51-year-old nonsmoking woman demonstrated progressive enlargement of a dominant nodule over 2 years, prompting video-assisted thoracoscopic segmentectomy. Histopathological examination in both patients confirmed DIPNECH, allowing for the exclusion of invasive malignancy and a comprehensive pathological assessment of neuroendocrine cell proliferation.

These cases illustrate a practical diagnostic challenge in patients with suspected DIPNECH who are asymptomatic. Although radiological surveillance is usually appropriate for indolent disease, the progressive enlargement of a dominant pulmonary nodule can limit the reliability of observation alone. Therefore, surgical resection can be justified as a diagnostic strategy within a multidisciplinary framework when malignancy cannot be confidently excluded, although careful patient selection and long-term surveillance remain essential.