Unexpected Autopsy Case of Placental Transmogrification of the Lung With Lipomatous Change With Detailed Immunohistochemical Analysis.

Placental transmogrification of the lung (PTL) is a rare cystic lesion characterized by a distinctive microscopic architecture resembling placental villi. Although its etiology remains unclear, PTL is frequently observed with emphysema, suggesting a potential association between these conditions. However, the precise nature of this relationship remains ambiguous, and whether PTL causes or results from emphysema remains unclear. This report presents an incidental finding of PTL without macroscopic emphysematous changes with detailed immunohistochemical and ultrastructural analysis. A 58-year-old man died from aspiration pneumonia due to methanol poisoning. Autopsy revealed pyothorax in the right lung cavity and hemorrhage in the bilateral putamen. Although the left lung showed no severe inflammatory changes, a white-yellowish granular lesion was observed. Histopathologically, the lesion demonstrated villi-like structures with interstitial adipocyte infiltration, without evidence of hamartomatous component, such as cartilage or smooth muscle. Thus, the lesion was diagnosed as PTL with lipomatous change. PTL is typically associated with emphysematous/cystic lesions and is often considered reactive due to these. Herein, the lesion was surrounded by microscopic emphysema, suggesting an early-stage PTL that may have contributed to the development of emphysematous changes. This report describes the PTL with detailed immunohistochemical analysis.