Abstract: Objective: To investigate the clinicopathological characteristics and differential diagnosis of invasive micropapillary carcinoma(IMPC) of the breast.Methods: The clinicopathologic information,histopathology and immunophenotype of 14 cases of IMPC of the breast were studied.Results: No special chinical symptoms or signs were observed in the cases.The occurrence of IMPC was 4.8%.The incidence of metastases of the lymph node(78.6%) and the number of metastatic node(on average 7.6) occurred more often in IMPC than that of the invasive ductal carcinoma(41.0%,on average 3.5).Histpathological features manifested that the nest of IMPC was pseudopapillary and was characterized by the tumor cells within artifical hollow space in clustered/tubular shape;the tumor cells were cylindercial or cubic,containing fine granular;the nucleus was oval,deep dyeing,mildly pleomorphic,and mitotic activity was rarely seen.Immunophenotype showed the toumor cells expressed an unique antistaining for epithelical membrance antigen(EMA),and part of the tumor cells expressed ER,PR or c-erbB-2.Conclusions: IMPC is a rare type of breast carcinomas,and its histopathologic feature is pseudopapillary nest of IMPC.The biological behaviour of IMPC is highly maliganant.More attentions should be paid to the differentiation of this tumor from invasive papillocarcinoma,mucinous carcinoma and metastatic carcinoma.