Abstract: Objective: To study the clinicopathologic characteristics,diagnosis and prognosis of lung adenocarcinoma with a micropapillary pattern (MPP).Methods: Four cases of lung adenocarinoma with MPP were retrospectively analyzed.The pathological features and the immnunotype were observed by light microscopy,and the literature was reviewed.Results: The clinical manifestations of lung adenocarcinoma with MPP were cough,expectoration and bloody sputum.Imaging findings demonstrated masses in the lung.Microscopically,the tumors consisted of variable proportion of corpora mammillaria cell clusters devoid of a fibrovascular core.By immunohistochemical staining,the tumor cells showed positive epithelial membrane antigen,E-cadherin,thyroid transcription factor-1 and cytokeratin 7;antigen (Ki-67) was highly expressed.The expressions of cytokeratin 20 and estrogen receptor were negative.The follow-up was two years on the average.Two of the cases developed hydrothorax and ascites six months after the operation,and the other two cases survived up to now with no distant metastasis.Conclusions: The content of MPP suggests invasion and metastasis of lung adenocarcinoma with MPP,which is an important factor influencing the prognosis.