Fatal cardiac inflammatory pseudotumor: a case report and literature review.

Inflammatory pseudotumor is a rare fibroinflammatory lesion described in nearly all organ systems, whereas cardiac involvement is exceptional. This case presents a sudden death due to cardiac inflammatory pseudotumor diagnosed at autopsy in an adult male with a recent diagnosis of Human Immunodeficiency Virus infection. Autopsy revealed cardiomegaly with asymmetric septal hypertrophy and an irregular tan white fibrous lesion infiltrating the interventricular septum. Histologic examination demonstrated replacement of myocardial tissue by a spindle cell mesenchymal lesion within a myxoid stroma, associated with extensive mixed acute and chronic inflammatory infiltrates, including plasma cells, lymphocytes, eosinophils, and macrophages, with involvement of the cardiac conduction system. Immunohistochemical studies supported the reactive nature of the lesion and excluded epithelial, myogenic, hematologic malignancies, and infective etiologies. Review of the literature identified six additional fatal cases of cardiac inflammatory pseudotumor diagnosed at autopsy between 1991 and 2021. In previously reported cases, the most frequent mechanism of death was arrhythmogenic, most often related to coronary artery involvement, although lesions affecting cardiac valves or the left ventricular outflow tract have also been described. In the present case, the location of the lesion within the interventricular septum, in close proximity to the cardiac conduction system, is most consistent with an arrhythmogenic mechanism of death. Identification of rare cardiac lesions at autopsy requires a thorough postmortem examination. In cases such as this, the use of immunohistochemistry is justified as a valuable ancillary tool in forensic pathology when needed to support interpretation and exclude alternative diagnoses.