Spindle cell/sarcomatoid metaplastic carcinoma of breast:a clinicopathologic and immunohistochemical analysis

Purpose To study the clinicopathologic and immunohistochemical features of metaplastic breast carcinoma with dominant spindle cell/sarcomatoid component(MBCSC).Methods Clinicopathologic data of 15 cases of MBCSC were analyzed.Immunohistochemical staining were performed in 12 cases(including epithelial markers,myoepithelial and tumor markers).Differences in axillary lymph node metastases,and the expression of ER,PR,Her2 were assessed between MBCSC and invasive ductal carcinoma(IDC).Results The mean age of the patients was 41 year-old.The main complain of all patients was noting a breast lump.Grossly,most tumors were well-circumscribed nodules.8 cases of tumors contained almost pure spindle cell,6 cases of tumors contained mainly spindle cell /sarcomatoid with a small area of IDC and 1 case of tumor with a little DCIS component.The tumors displayed moderate-high grade of histological morphology.11/12 cases(91.7%) of spindle cell/sarcomatoid components were positive for at least one epithelial markers.All cases of spindle cell expressed at least one or more than one myoepithelial markers.The rate of axillary lymph node metastases and the expression of ER,PR,Her2 were lower in case group than that in control group.Conclusions MBCSC exhibits characteristically histopathologic morphology and myoepithelial differentiation,with the biologic features such as the axillary lymph node metastases and the expression of tumor markers were different from IDC,suggesting an independent pathologic subtype.Immunohistochemical staining of series of epithelial and myoepithelial markers could contribute to the pathologic diagnosis.