IL-6 cytokine family is composed by several members. IL-6, LIF, and gp130 have been associated with cancer progression. Cytokines play an important role in tumoral growth, invasion of the vessels and development of metastases. Immunoexpressions of LIF, OSM, LIFRbeta and OSMRbeta were studied in benign breast lesion, in situ and infiltrating tumors by Western blot and immunohistochemistry. Percentages of positive samples to OSM, LIF and OSMRbeta were higher in in situ carcinoma than in benign diseases and even higher in infiltrating tumors. gp130-positive samples was higher in infiltrating tumor than in benign diseases. All samples studied were LIFRbeta-positive. Infiltrating tumors showed the most intense immunostaining to LIFRbeta, OSM and OSMRbeta; comparing present results revealed an association between the expression of these proteins and increasing malignancy. In conclusions, development of breast tumor increases the expression of OSM, LIF, OSMRbeta, LIFRbeta and gp130, and this expression may be associated with the malignancy. IL-6 family exert their action through transducer receptor gp130, and gp130 expression increase with malignance, it might be a crucial point in the development of infiltrative adenocarcinoma. The secretion of OSM and LIF by both epithelial and stromal (paracrine manner) cells seems to promote tumor growth.