Precancerous Lesions of the Breast.

B3 lesions represent 3–10% of the histologically assessed lesions in mammography screening. They comprise different histopathological entities which provide benign histology, but are either known to show heterogeneity or to have an increased (albeit low) risk of associated malignancy, e.g. FEA, ADH, lobular neoplasia (LN), papillary lesions, radial scar, and phyllodes tumor. With regard to the differing cancer risk of these lesions, the authors demonstrate that many factors need to be considered to find an individually adapted recommendation for each patient. Avoidance of resecting too often and too much on the one hand, or resecting too seldom and too little on the other, requires an interdisciplinary team that takes into account and weighs all available information: biological risk, representative sampling, lesion size, and lesion extent, percentage of lesion removal, other individual risks and the possibility of surveillance. But the biological and clinical significance of some of these lesions remains to be clarified. It is evident that the neoplastic process begins earlier than at the DCIS stage, but which histological lesions are directly involved in this process and what drives them in progression is not fully understood. Sinn et al. [5] give an illustrative review of those lesions that today are thought to represent the earliest neoplastic lesions that are related to the low-grade pathway of breast cancer development: FEA, ADH and LN. The presented molecular findings and clinical studies demonstrate that these lesions are both early precursor lesions and indicators for an increased ipsiand contralateral cancer risk. However, the controversy and uncertainty about the biological significance of these lesions still remains. This is also reflected in the varying terminology used in the literature and the lack of generally accepted criteria that are highly reproducible [3, 6–9]. In consequence, the intraobeserver variability of these lesions is higher than in DCIS or invasive breast cancer. With account to these restrictions, Sinn et al. [5] summarize our current understanding of these lesions and add some advice for subtle management. Since mammography screening has been implemented in many countries, DCIS has been given a great deal of attenThe introduction of mammography screening has caused an increased detection of precancerous lesions. Nowadays, ductal carcinoma in situ (DCIS) accounts for up to 25% of all newly diagnosed breast cancer cases in screening regions [1, 2]. Furthermore, mammography screening has attracted attention to a variety of early precursor lesions that have been observed before at most as an accompanying finding in the vicinity of invasive breast carcinomas. These include intraductal proliferative lesions with atypia like flat epithelial atypia (FEA) and atypical ductal hyperplasia (ADH). The detection of these lesions in large core needle biopsies, used for the histological assessment of suspect mammographic lesions, especially microcalcifications, has brought about questions regarding their biological significance and practical management. They represent a broad spectrum of lesions with variable risk of progression. Nowadays it is not possible to identify with absolute certainty which of these lesions will progress and which not. The uncertainty how to handle them adequately is reflected in the histological classification used in mammography screening where these lesions are categorized as ‘B3: lesions of uncertain malignant potential’ [3]. Tailoring the treatment of precancerous lesions according to each individual case is a multidisciplinary challenge, which involves radiologists and pathologists as well as breast surgeons and, in case of DCIS, radio-oncologists and medical oncologists. There is a particular dilemma to balance the risk of causing unnecessary overtreatment or leaving an increased risk of recurrence or progression. Therefore, this issue of Breast Care addresses the topic of precancerous lesions in a multidisciplinary approach. Experts from the involved disciplines give a summary of the current knowledge about the evolution, diagnosis, and management of precancerous lesions. The aim is to improve our understanding and handling of these heterogeneous lesions by bringing together the different perspectives. The prevalence, radiological appearance and assessment procedure of those lesions categorized as B3 in percutaneous breast biopsies is addressed by Heywang-Köbrunner et al. [4].