Ductal carcinoma in situ (DCIS) now accounts for 20-30% of all newly diagnosed breast cancers in centers which use mammographic surveillance as a standard part of the examination. The majority of these DCIS lesions, at least in the United States, are of very limited size, with mean estimated extents of 8-20 mm, based on pathological examination. A small fraction of these are incidental microscopic features of the biopsy; the majority are detected on the basis of mammographic microcalcifications.
These mammographically detected DCIS lesions are biologically heterogeneous, and this is reflected by their histology. Moreover, a number of recent independent studies have shown that the clinical outcome of patients, particularly those treated by breast conservation, is related to the presence of reproducible and identifiable histologic features, and possibly to certain immunohistochemically demonstrable gene markers as well.
Regardless of the type of therapy, local recurrence in the breast is the most common and often the only site of failure after breast conservation therapy for X I S . Although individual studies show some variation in the proportion of invasive to non-invasive recurrence, equal numbers of invasive and non-invasive recurrences are most commonly noted.