February 2025—Pulmonary complications cause significant morbidity and mortality in post-hematopoietic stem cell transplantation. The histopathology of pulmonary diseases in the context of post-hematopoietic stem cell transplantation (post-HSCT) is poorly characterized, especially in the pediatric population. The authors sought to characterize the pathologic spectrum of pulmonary disease post-HSCT in a pediatric cohort. Fifty-six specimens, including 53 biopsy specimens, corresponding to 53 patients were identified. Biopsy slides were reviewed and assigned to diagnostic categories (infectious, graft-versus-host disease, vasculopathy, indeterminate, and others) by consensus among three pediatric pulmonary pathologists, taking into consideration pathologic, clinical, radiologic, and laboratory findings.