Pulmonary lymphangiomyomatosis: three new cases studied with electron microscopy.

Three cases of pulmonary lymphangiomyomatosis are described, with emphasis on the ultrastructural changes. The clinicopathologic features corresponded to those previously described. Each patient was a female in the reproductive years; breathlessness and recurrent pneumothoraces were the predominant clinical features. Histologically, the lungs showed a focal interstitial infiltrate of short, spindle-shaped mononuclear cells compatible with primitive smooth muscle, which was associated with irregular emphysema and hemosiderosis. Electron microscopy confirmed the smooth muscle nature of the pulmonary infiltrate and showed the presence of cells intermediate between smooth muscle and fibroblasts. Abnormalities were also noted in the pulmonary connective tissue that are possibly related to the fragility of the lung in this condition.