Diffuse idiopathic pulmonary cell hyperplasia diagnosed by navigational bronchoscopy

SESSION TITLE: Lung Pathology: Show and Tell SESSION TYPE: Case Reports PRESENTED ON: 10/08/2023 10:45 am - 11:45 am INTRODUCTION: Diffuse idiopathic pulmonary neuroendocrine hyperplasia (DIPNECH) is a rare idiopathic airway syndrome typically with insidious onset with characteristics of obstructive airways disease, and is often misdiagnosed. Pulmonary neuroendocrine cells make up less than 1% of adult bronchiolar cells and are involved in development and are in adults are thought to be involved in airway responsiveness to environmental factors. Given that DIPNECH considered a pre-malignant condition and can be highly symptomatic, it is important to distinguish this from other conditions as well as neuroendocrine hyperplasia reactive to environmental factors, chronic infections and underlying inflammatory conditions. CASE PRESENTATION: Our patient was a 49-year-old female never smoker referred to our interventional pulmonary clinic for navigational bronchoscopy for many small progressively enlarging peribronchiolar and peripheral pulmonary nodules over 6 months associated with worsening dyspnea with ambulatory desaturation. Her pulmonary function tests did not reveal overt obstruction, but she had notable air trapping and small airways response to bronchodilators. Her PET scan was negative for hypermetabolic lesions and her echocardiogram and myocardial perfusion scans were normal. Her rheumatologic and infectious serologies as well as IgG subclasses and chromogranin A were normal. She underwent navigational bronchoscopy with needle aspiration and biopsies of 2 left-sided nodules smaller than 1 cm in size. Bronchiolar lavage was negative for infection and surgical pathology revealed nodular neuroendocrine cell proliferation consistent with DIPNECH given the presence of many nodules. Given some nodules were greater than 5mm on CT scan there was the possibility of neuroendocrine tumor, though the aggregate biopsy sample was less than 5mm. Immunohistochemistry demonstrated a low mitotic rate and her dotatate PET was without abnormal uptake. She underwent surveillance with thoracic oncology and remains on a fluticasone inhaler, which has been controlling her symptoms. Somatostatin analog therapy is being considered if she develops worsening symptoms of dyspnea or obstructive lung disease. DISCUSSION: Surgical lung biopsy is currently considered the gold standard for diagnosis and may be preferable for larger carcinoid tumors. Our case demonstrates the utility of navigational bronchoscopy in acquiring a biopsy of small bronchiolar nodules that characterize DIPNECH. Integrating history, pulmonary function testing, and histology of transbronchial samples found with this technique with the radiologic patterns and size of nodules seen on CT, PET and dotatate PET can enable clinicians to distinguish between reactive neuroendocrine cell hyperplasia, DIPNECH, tumorlet, and carcinoid tumor. CONCLUSIONS: Navigational bronchoscopy can be particularly useful in diagnosing DIPNECH given small size and peripheral location. Further research is needed to compare yield and procedural risks and cost of navigational bronchoscopy with traditional methods such as transbronchial lung biopsy and surgical lung biopsy. REFERENCE #1: Rossi, G, Cavazza, A, Spagnolo, P, Sverzallati, N, Longo, L, Agita, J, Montanari, G, Carbonelli, C, Vincenzi, G, Bogina, G, Franco, R, Tiseo, M, Cottin, V, Colby, TV. Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia syndrome. European Respiratory Journal 2016 47: 1829-1841; REFERENCE #2: Little, BP, Junn, JC, Zheng, KS, Sanchez, FW, Henry, TS, Veeraghavan, S, Berkowitz, EA. Diffuse Idiopathic Pulmonary Neuroendocrine Cell Hyperplasia: Imaging and Clinical Features of a Frequently Delayed Diagnosis. Journal of Roentgenology. 2020;215: 1312-1320. REFERENCE #3: Almquist, D, Cabrera, A, Sonbol MB, Kosiorek, HE, Halfdanarson, TR, Ross, HJ, Paripati, H, Jaroszewski, DE. DIPNECH: The Mayo experience.Journal of Clinical Oncology 2019 37:15_suppl, e20029-e20029 DISCLOSURES: No disclosure on file for Mohit Chawla No relevant relationships by Kimia Ganjaei