Case report: Pulmonary extranodal mucosa-associated lymphoid tissue lymphoma with eosinophilia diagnosed via exclusion using metagenomic next-generation sequencing.

Pulmonary extranodal mucosa-associated lymphoid tissue lymphoma (MALToma) is a slow-growing lymphoma often misdiagnosed or undiagnosed due to its nonspecific clinical symptoms. A man in his late 30s initially presented with cough, sputum production, and chest pain, which improved after antibiotic treatment. A definitive diagnosis of pulmonary MALToma was established via bronchoscopic biopsy. Following the exclusion of alternative diagnoses through metagenomic next-generation sequencing of bronchoalveolar lavage fluid, the marked eosinophilia and diverse chest computed tomography findings highlight the need for clinical awareness of this disease.