PD-1/PD-L1 negative schwannoma mimicking obstructive bronchial malignancy: A case report.

Schwannomas are homogeneous tumors of schwann cells and occur at peripheral and cranial nerves on the upper limbs, the head and neck area. Rarely, a bronchial schwannoma may appear in the lung and be misdiagnosed as lung neoplasms. Here, we report a 56-year old woman with a 5.8 x 7.0 x 2.8 cm lesion in her right upper lobe bronchus. The lesion had a maximum standardized uptake value (SUVmax) of 8.5 by 18-fluorodeoxyglucose positron emission tomography (FDG-PET). Bronchoscopy showed a mass obstructing the bronchus that bled easily. Despite repeated biopsies, a lung malignancy could not be excluded, and surgical resection was subsequently performed. Pathological examination demonstrated a primary bronchial schwannoma that was positive for molecular markers S-100 and SOX-10, negative for immune checkpoint marker PD-1/PD-L1 but also demonstrated certain uncommon pathological features. This case highlights the heterogeneity of bronchial masses and the diagnostic challenge for differentiating benign and malignant tumors in the thorax. Key points Rare bronchial schwannoma mimics lung malignancy and poses a diagnostic challenge. This case of bronchial schwannoma, unlike peripheral schwannoma, lacks PD-L1. Pathological features indicate autonomic nerve origin for pulmonary schwannomas.