Occult Neoplasms in Sudden Unexpected Death in Infancy: A Scoping Review of Post-Mortem Findings

Background: Sudden unexpected death in infancy (SUDI) may occasionally be attributable to neoplasms that were clinically unrecognised before the terminal event and diagnosed or confirmed during post-mortem investigation. These occult neoplasms are exceptionally rare and remain poorly characterised. This scoping review identifies published reports of neoplasms not diagnosed or strongly suspected before the terminal event in infants who died suddenly and unexpectedly, and systematically collects data on pathological features, diagnostic modalities, mechanisms of death, and the extent to which the neoplasm contributed to death. Methods: A search of PubMed/MEDLINE and Scopus was conducted without a lower publication-date restriction through 19 July 2026, in accordance with Joanna Briggs Institute guidance and PRISMA-ScR. Publications describing sudden unexpected deaths in infants younger than 12 months with a previously undiagnosed neoplasm were selected and reviewed. Findings were extracted, and deaths were classified according to whether the neoplasm was causal, contributory, or incidental to death. Results: Twenty-five studies comprising 32 infant cases were included in the review. The median age at death was 2.5 months. The most frequent lesions were cardiovascular or thoracic neoplasms (16/32), followed by haematological or lymphoid neoplasms (6/32). Sixteen lesions were benign, ten were malignant, and six were intermediate, uncertain, or tumour-like. Twenty-five neoplasms were evident on macroscopic examination, whereas seven were identified only histologically. Reported mechanisms of death included arrhythmia, mechanical obstruction, respiratory failure, haemodynamic compromise, haemorrhage, leukostasis, and diffuse infiltration. Within the published cases included in this review, the review team classified the neoplasm as causal in 16 cases (16/32, 50.0%), contributory in 13 cases (13/32, 40.6%), and incidental in three cases (3/32, 9.4%). Conclusions: Autopsy examination is critical for identifying previously undiagnosed neoplasms, which are rare but potentially important findings in the investigation of SUDI. Among the selected published cases included in this review, the review team classified the neoplasm as causal in half of cases; this proportion should not be extrapolated to the broader SUDI population. Comprehensive autopsy assessment of SUDI cases, including thorough histological sampling and ancillary testing, is therefore essential for determining the role of a tumour in infant death.