Introduction: Breast cancer is the most common women cancer. According to recent data, in Poland, in 2007 there were 14,482 new cases and 5255 deaths due to cancer. As a result of tumor progression the basement membrane (BM) have been damaged. BM is a fundamental barrier that separates the cell from epitelialne extracellular matrix (ECM).Th e main component of BM is collagen IV. Collagen IV is one of the regulators in the induction of expression of estrogen receptors α and β (ER β in the membrane of tumor cells. Th e presence of ER β encourages the development and proliferation of cancer cells.Objective: Th e aim of this study was to examine the relationship between the expression of collagen type IV and the presence of estrogen receptors in tumor and normal breast tissue. Results: It was a higher expression of collagen IV, both in tumor and normal tissue in patients with positive estrogen receptor, compared with patients without estrogen receptors. Conclusions: The relationship found expression of collagen IV, the presence of estrogen receptors in tumor tissue and tissue which were histopathologically identifi ed as normal, from the margins of surgically removed breast cancer.