Ultrastructure of the proliferating cells in pulmonary lymphangiomyomatosis

Pulmonary lymphangiomyomatosis occurs almost exclusively in women and is characterized by a widespread proliferation of spindle-shaped cells within the lung. Although these cells have been considered to be vessel-associated smooth muscle cells, their origin remains undefined. In this case of pulmonary lymphangiomyomatosis studied by electron microscopy, the proliferating cells were found to vary morphologically and to differ from typical smooth muscle cells. The ultrastructure suggests that the cell of origin might be the pulmonary interstitial cell rather than vascular smooth muscle. It is also possible that the cells are derived from pericytes. Accumulations of glycogen were seen in the proliferating cells and are suggested to be a reflection of an estrogenic hormonal dominance.