Jacky Luiten

Introduction and outline | 9 1 In an effort to detect breast cancer in its earliest phase, any breast abnormality found at screening mammography is examined in detail which results in an increased detection rate of DCIS and other pre‐malignant diseases. In the absence of screening, a substantial part of these pre‐malignant abnormalities would have remained subclinical without proceeding to invasive breast cancer during a woman’s lifetime. 19,20 As a consequence, screening results in overdiagnosis and subsequent overtreatment, which is one of its primary harms. Another downside are the false positives recalls, of which not only the costs and psychological stress, but also the potential burden of subsequent unnecessary invasive biopsies must not be overlooked. 21 A careful consideration of the harm‐benefit balance associated with breast cancer screening continues to be a matter of debate. Outline of thesis This thesis describes the trends in confirmation and treatment of pre‐malignant abnormalities at screening mammography. Pre‐malignant breast lesions were defined as DCIS and high‐risk lesions. High‐risk lesions were defined as lesions that do not have reached the phase of invasive disease but on the other hand do not show full similarity with normal breast tissue. Examples are flat epithelial atypia, atypical ductal hyperplasia, lobular carcinoma in‐situ, papillary lesions. Chapter 2 analyzes the trends in incidence of screen‐detected DCIS and invasive carcinoma prior, during and after the transition from SFM to FFDM. Considering the possibility that low grade DCIS may preferably develop into low grade invasive carcinoma and high grade DCIS to high grade invasive carcinoma, the correlation between screen‐detected DCIS and invasive breast cancer classified by grade was investigated. A representative biopsy of a suspicious abnormality detected at screening mammography is required to obtain a definitive histopathology result. Surgical excision biopsy, which is an invasive technique, used to be the most reliable method to obtain a conclusive diagnosis. 22 However, a decline in the use of surgical excision biopsies has been described until 2010, caused by the introduction and widespread use of stereotactic core biopsy (SCNB) and it has been postulated that surgical excision biopsies would become an obsolete procedure in the years thereafter. 23 The aim of chapter 3 was to investigate the more recent trends in the use and