Abstract

Histopathology of pulmonary lymphangioleiomyomatosis(LAM) is studied using four new cases and six previously reported cases, which include two cases without definite evidence of LAM. The important diagnostic features of this lesion were nodular proliferation of immature smooth muscle and cleft or cyst formation within the nodules of smooth muscle cells. The nuclei of the smooth muscle cells were bigger than those of blood vessels or fibrotic lung, and the direction of nuclei was irregular. The lung parenchyma showed little inflammatory change but there were multiple air cysts with smooth muscle nodules at their margin. There were two cases with exuberant proliferation of smooth muscle nodules and two cases with papilliferous projections of the cells into lymphatic lumen. Whereas, three cases had only a few small slender nodules of smooth muscle cells at the margin of air cyst. The lymphatic lumen with smooth muscle nodules is dilated in four cases but other four cases show collapsed lumen. Pulmonary hemorrhage and hemosiderosis were prominent in three cases. There were variety of histology in terms of the cellularity of smooth muscle nodules, the size of the lymphatic lumen and the degree of pulmonary destruction, which may have significance on the clinical presentation and prognostication.

• Keywords: Lymphangioleiomyomatosis;Chylothorax;Pulmonary fibrosis;Emphysema