Spontaneous Regression of Relapsed CNS Neuroblastoma, FOXR2‐Activated, Temporally Associated With Postoperative Pyoderma Gangrenosum

Central nervous system (CNS) neuroblastoma, FOXR2-activated (CNS NB-FOXR2), is a rare pediatric embryonal tumor recognized in the 2021 World Health Organization Classification of Central Nervous System Tumors, with genome-wide DNA methylation profiling supporting its classification [ 1-3 ].We report a child with relapsed CNS NB-FOXR2 who experienced resolution of spinal metastatic disease and involution of the residual primary tumor without salvage therapy.Regression occurred during severe postoperative inflammation later diagnosed as pyoderma gangrenosum (PG), an autoinflammatory neutrophilic dermatosis [ 4 ].This temporal association raises the possibility that systemic inflammation contributed to tumor regression.