Idiopathic Diffuse Pulmonary Neuroendocrine Cell Hyperplasia Associated with Twenty-Three Synchronous Typical Pulmonary Carcinoid Tumors in an Asymptomatic Patient: A Case Report

Abstract

Introduction: Idiopathic diffuse pulmonary neuroendocrine cell hyperplasia (DIPNECH) is a rare disease recognized as a precursor lesion of pulmonary neuroendocrine tumors. Its association with multiple synchronous pulmonary carcinoid tumors is exceptionally uncommon. The aim of this report is to describe the radiological and histopathological features that led to the diagnosis of DIPNECH in an asymptomatic patient. Case Presentation: A 70-year-old non-smoking woman with a history of cardiovascular disease and hypothyroidism was found to have an incidental 13-mm solid pulmonary nodule in the left lower lobe. Positron emission tomography demonstrated mild metabolic uptake, and follow-up imaging showed progressive growth. The patient went under a video-assisted thoracoscopic (VATS) left lower lobectomy with mediastinal lymph node dissection. Histopathological analysis identified twenty-three synchronous pulmonary neuroendocrine tumors, classified as  grade 1 typical carcinoids measuring 2-11 mm, with a Ki-67 proliferation index of 2% and no lymph node involvement. Radiologic-pathologic correlation established the diagnosis of DIPNECH associated with multiple synchronous typical pulmonary carcinoid tumors. Discussion: DIPNECH is infrequent and underdiagnosed. Although its association with pulmonary carcinoid tumors has been well documented, the presence of twenty-three synchronous typical carcinoids in an asymptomatic patient is exceptional. This case shows the value of recognizing radiological findings suggestive of DIPNECH, particularly the simultaneity of multiple pulmonary micronodules and a mosaic attenuation pattern, which may precede a histopathological diagnosis. Early identification of these signs may facilitate diagnosis and contribute to timely management.