High-Grade Malignant Pleuropulmonary Neoplasm With <i>YAP1::MAML2</i> 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 <i>YAP1::MAML2</i> gene fusion and a complex copy number profile, with no mutations in <i>DICER1</i> or <i>TP53</i>. 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 <i>YAP1::MAML2</i> fusion in a pleuropulmonary neoplasm.