B80-5-02 Defined by Histology, Undefined by Therapy: The Ongoing Challenge of Dipnech

Abstract Introduction Diffuse Idiopathic Pulmonary Neuroendocrine Cell Hyperplasia (DIPNECH) is a rare pre-malignant condition precursor to pulmonary carcinoid tumors and tumorlets with or without bronchiolitis obliterans. It arises from diffuse proliferation of bronchial and bronchiolar neuroendocrine cells and typically affects nonsmoking women in their sixth decade. Presentations range from chronic cough and dyspnea to progressive airflow obstruction, sometimes culminating in bronchiolitis obliterans. Case Presentation A 76-year-old woman with chronic bronchitis, and 35-year tobacco abuse was referred to the pulmonology clinic after a lung cancer screening CT showed a 3.5 cm mass in the right middle lobe, and numerous bilateral pulmonary nodules in a mosaic attenuation pattern. Symptoms included a cough with scant, purulent sputum. A tissue diagnosis was obtained with biopsy via navigational bronchoscopy. Histopathology was consistent with a neuro-endocrine proliferation without high-grade features. Immunostaining was positive for CAM 5.2, INSM1, and chromogranin, and negative for p40, consistent with a diagnosis of DIPNECH given the size of the mass. A staging dotatate PET-CT scan had somatostatin-receptor avidity (Figure1). Patient was offered the options including surgery and SBRT and was referred to thoracic surgery per preference and underwent right middle lobectomy. Discussion In our case radiologic findings of multiple bilateral nodules with mosaic attenuation raised the suspicion for DIPNECH prior to histopathologic confirmation.” Histopathology is the gold standard. Marchevsky and Walts proposed diagnostic criteria requiring 5 neuroendocrine cells in at least three small airways with ≥3 carcinoid tumorlets, though consensus remains lacking. There are no current guidelines for standard therapies, and treatment is highly individualized, usually involving the management of airway disease with bronchodilators and steroids. Azithromycin has been used for its known anti-inflammatory properties in airway management. Approximately 30-50% of patients with DIPNECH may develop carcinoid tumorlets or overt carcinoid tumors over time, but these are typically well-differentiated, low-grade lesions with excellent outcomes after resection. The NCCN now recommends somatostatin analogs. There have been case reports of treatment with mTOR inhibitors, such as everolimus and tacrolimus. Complete surgical resection is offered based on progression and size; in a few cases, radiation therapy has been used in cases where surgery wasn’t an option. Outcomes of SBRT in other bronchial carcinoids have been favorable. Conclusion DIPNECH poses both diagnostic and therapeutic challenges. Despite growing recognition of its characteristic features, treatment remains largely empirical. Collaborative data collection and prospective studies are needed to establish standardized management for this rare but clinically significant disease. This abstract is funded by: NA