3.3 Pathological examination
All the patients were treated with surgery. The resected affected site was the right lower lobe in 50% (3/6), patients the right upper lobe in 16.7% (1/6) patient. However, there are 33.3% (2/6) patients (No.3 and No.5) affected both lung lobes, the resection of right lower lobe was made in patient No.3, and the resection of left lobe was made in patient No.5.
The gross specimens showed multiloculated cysts with variable size within the pulmonary parenchymal, and the cysts had a smooth inner surface. Some cysts contained a small amount of clear fluid.
Histological examination showed that the walls of the cysts were adjacent to interlobular septa or bronchovascular bundles, the wall of cysts was composed of a thin layer of fibrous tissue, and the thin band of fibrous tissue was discontinuous. Small collections of uninucleated and multinucleated macrophages were lined in the surface of the main cysts (Fig. 2 and Fig. 3) . The giant cells contained from 2 to 40 centrally placed nuclears.
The adjacent parenchymal surrounded the cysts showed mild to marked atelectasis and inflammatory cells infiltrates in all cases(Fig. 2 and Fig. 3) , containing histocytes, lymphocytes, plasma cells, and neutrophils, indicating there were inflammation along the cysts.