Diffuse striated muscle heteroplasia of the lung. An autopsy case.

We studied a diffuse, striated muscle heteroplasia in the lungs in a 20-week-old stillborn fetus. The lung was small, but retained normal shape. There was no tumefaction. Histologically, a massive and diffuse distribution of the striated muscle cells was found among the interstitia of the dysplastic lung, representing solid adenomatoid malformation. Based on the findings in this case and the cases of others, we believe that the presence of the striated muscle and adenomatoid malformation are causally related, and the striated muscle cells arise from the heteroplastic transformation of the pluripotential embryonal mesenchymal cells.