Breast cancer is one of the most common cancers to complicate pregnancy. Up until recently, such diagnosis was almost invariably bound with an abortion with all its possible psychological and ethical consequences for the patient, her family, and treating physicians. Throughout the past few years, the considerable progress in medical knowledge and experience has allowed a radical change in the situation of this very special patient group. These days, women may continue with the pregnancy, yet at the same time be effectively and safely treated, in a very close adherence to standards applied in the treatment of non-pregnant patients. The diagnostics of breast cancer in pregnant patients largely meets the generally accepted standards of detecting and staging the disease, apart from a few exceptions mostly related to fetus safety. The differences concern e.g. the sentinel lymph node evaluation procedure and some imaging methods. Whether the patient qualifies for treatment as well as therapeutic decisions depend on the gestational age and the advancement of the disease, with some treatment procedures imperatively postponed until postpartum. Certain chemotherapy regimens have been proved safe during pregnancy, even though up until recently they were considered toxic and impossible to use (FAC, FEC, taxoids). It has also been shown that, unless obstetric indications for caesarean section exist, in most cases the pregnancy does not need to be terminated prematurely. No oncologic counter-indications for a vaginal delivery exist either. This paper aims to bring together and sum up the body of knowledge arising from the recent publications which have facilitated diagnostic and therapeutic standards to be followed in these infrequent, yet exceedingly complex, clinical situations.