Introduction: Pulmonary hypoplasia is common in the perinatal period and a significant cause of death in newborn infants. The majority of patients present with severe respiratory distress or repeated pulmonary infections. However, there have been some cases of pulmonary hypoplasia being diagnosed in adulthood. Furthermore, there have been some reports of lung cancer and Diffuse Idiopathic Pulmonary Neuroendocrine Cell Hyperplasia (DIPNECH) developing in pulmonary hypoplasia patients.

Case Presentation: A 70-year-old man was aware of dry cough. Chest computed tomography showed a ground-glass nodule in the upper lobe of the right lung and middle lobar incomplete development of the right lung. Lung cancer of the right upper lobe and pulmonary hypoplasia of the right middle lobe was suspected, and right upper and middle lobectomy and lymph node dissection were performed. A pathological examination confirmed lepidic adenocarcinoma of the right upper lobe and a well-differentiated neuroendocrine tumor with an organoid or trabecular pattern at the middle lobe of the right lung. Based on the results of an immunohistochemical study, the tumor of the middle lobe was diagnosed as typical carcinoid.

Conclusion: We experienced a rare case of pulmonary typical carcinoid in a patient with middle lobe hypoplasia of the right lung coexisting with lung adenocarcinoma on the upper lobe of the right lung.

Keywords: Pulmonary hypoplasia; Carcinoid; Lung cancer; Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia