Histogenesis of the so‐called “intravascular bronchioloalveolar tumour”

Abstract

Three cases of Dial and Liebow''s intravascular bronchioloalveolar tumor are described, with emphasis on ultrastructure and histogenesis. The tumor cells are quite different from adjacent reactive alveolar cells and EM does not support the suggested alveolar cell origin. The tumor cells contain abundant microfilaments, moderate amounts of rough endoplasmic reticulum and varying numbers of Weibel-Palade bodies. With features of smooth muscle, myofibroblast and endothelial cell differentiation, a vascular origin from precursor mesenchymal cells, such as the vasoformative reserve cells, is suggested.