Forensic evidence from a 30-year study of non-thrombotic pulmonary embolism

Non-thrombotic pulmonary embolism (NTPE) represents a heterogeneous and underrecognized group of conditions characterized by the obstruction of the pulmonary vasculature by non-thrombotic material, often associated with complex pathogenetic mechanisms and non-specific clinical presentations. Despite their potential to cause sudden and unexpected death, comprehensive forensic studies on NTPE remain limited. This study presents a 30-year retrospective forensic analysis (1993-2024) of autopsy cases performed at the Institute of Legal Medicine of Milan, aimed at identifying and characterizing deaths attributable to NTPE. Among 325 fatal pulmonary embolisms, 32 cases (9.8%) were classified as NTPE. Bone marrow embolism was the most frequent subtype (37.5%), followed by septic (25%), fat (21.8%), and amniotic fluid embolism (9.4%), with single cases of air and neoplastic embolism. NTPE occurred predominantly in traumatic and iatrogenic settings and were frequently associated with surgical or invasive procedures. Macroscopic findings were often non-specific, whereas histopathological examination proved decisive for diagnosis, frequently requiring targeted histochemical techniques to identify the nature of the embolic material. These findings highlight the intrinsic diagnostic complexity of NTPE and the risk of under recognition in the absence of systematic post-mortem investigation. In this context, a comprehensive forensic autopsy approach remains essential for the accurate identification and classification of these entities. Increased awareness of NTPE, together with the integration of histopathological and ancillary analyses, may contribute to improving diagnostic accuracy and to a more reliable interpretation of sudden and unexpected deaths.