High-Grade Malignant Pleuropulmonary Neoplasm With YAP1::MAML2 Gene Fusion

A 17-month-old male presented with a 4-week history of cough, and a CT scan revealed a large right intrathoracic mass with metastases to the brain and femur. Tumor biopsy demonstrated a high-grade malignant neoplasm with histological and immunostaining features most suggestive of, but not entirely typical for type III pleuropulmonary blastoma (PPB). Molecular analysis identified a YAP1::MAML2 gene fusion and a complex copy number profile, with no mutations in DICER1 or TP53. The patient initially improved with chemotherapy, but progressive brain metastases led to palliative care, and he passed away 10 months later. This is the first reported case of a YAP1::MAML2 fusion in a pleuropulmonary neoplasm.