Description:
<jats:p> <jats:bold>Background</jats:bold>: All cases of <jats:italic>in situ</jats:italic> and invasive breast cancer are reported to the Victorian Cancer Registry. In 1988 a special subregister of all cases of carcinoma <jats:italic>in situ</jats:italic> and small invasive cancers up to 10 mm in size was established – the In situ and Small Invasive Breast Cancer Register (ISSIBCR). This was unique in being a population‐based register and only possible because in Victoria, as in some other Australian states, all cancers including <jats:italic>in situ</jats:italic> disease are reported to the Central Cancer Registry.</jats:p><jats:p> <jats:bold>Methods</jats:bold>: Between 1 January 1988 and 31 December 1992, 517 cases of <jats:italic>in situ</jats:italic> cancers and 892 invasive cancers of ≤ 10 mm in diameter were registered. During the study period, mammography screening was progressively introduced in Victoria and the number of cases, in both categories registered annually, doubled.</jats:p><jats:p> <jats:bold>Results</jats:bold>: The method of detection, the pathology and treatment of these lesions are described. It is of interest that 46.5% of the in situ cancers and 68.8% of the invasive cancers were detected either by the patient or her doctor on clinical examination. Total mastectomy was the method of treatment in 35.4% of in situ cancers and 42.0% of small invasive tumours. Only 38.0% of patients with small invasive cancers treated by breast‐conserving surgery had irradiation of the affected breast.</jats:p><jats:p> <jats:bold>Conclusions</jats:bold>: This register provides a valuable resource for the follow up of the natural history and outcome of treatment of the affected women.</jats:p>