Abstract
A term male neonate was delivered at 37 weeks and 3 days gestation in April 2025 via urgent caesarean section due to non-reassuring fetal heart tones. At birth, an unanticipated large right-sided cervical mass caused immediate respiratory distress, necessitating emergent endotracheal intubation. Within the first 24 hours of life, the infant developed spontaneous tumour lysis syndrome (TLS) with severe electrolyte derangements, metabolic acidosis and profound cardiac dysfunction, a phenomenon that has been rarely described in neonates with congenital malignancies. Imaging revealed a cervical mass with mediastinal extension and hepatic metastases. Core biopsy confirmed International Neuroblastoma Risk Group stage MS neuroblastoma, corresponding to historic International Neuroblastoma Staging System stage 4S, MYCN non-amplified, with favourable histology. Multidisciplinary management included airway stabilisation, TLS-directed therapy and early chemotherapy, resulting in rapid metabolic stabilisation and tumour regression. The infant was discharged on day 44 with improving respiratory status and ongoing outpatient oncology follow-up. This case emphasises the need for rapid recognition of TLS in congenital malignancies and coordinated airway and oncological care.