DUCTAL CARCINOMA IN SITU PART I: DEFINITION AND DIAGNOSIS

The frequency of diagnosis of ductal carcinoma in situ (DCIS) has increased in Australia, largely because of the national screening programme. Ductal carcinoma in situ presents a dilemma because of problems with its diagnosis and variations in reporting pathological and radiological findings, making it difficult to define optimal treatment and communicate information in a way that helps the patient understand the problems and make decisions. There is considerable inter-observer variation, particularly in differentiating low-grade DCIS from ductal hyperplasia, with or without atypia, but pathologists who participate in regular pathological review sessions vary less in their opinions. Mammography remains the main investigative tool for DCIS and the American College of Radiology has recommended standardized reports. A team approach is required for the removal and diagnosis of possible DCIS. Although the team may be best co-located in the one facility, this is not practical in many community hospital settings which lack on-site radiology and pathology services. The decision about how much breast tissue to remove will need to be made for each patient and depends on the size of the microcalcification and how suspicious the mammogram is for DCIS. We recommend the use of synoptic reports for DCIS, and we document the minimum factors that should be reported by pathologists. The evaluation and management of DCIS by a multidisciplinary team will allow the patient access to information required to make often difficult treatment decisions. In this paper, we review the literature about the natural history, pathology, cytology and radiology of DCIS and document the 20 critical steps required for the diagnosis of impalpable, mammographic microcalcifications suspected to be DCIS.