Pathology of ductal carcinoma in situ of the breast: a heterogeneous entity in need of greater understanding.

Breast cancer is the commonest malignancy among Singapore women. Ductal carcinoma in situ (DCIS) is the putative precursor of the majority of invasive breast cancers, and its incidence has increased dramatically with mammographic screening. It is a heterogeneous disease--radiologically, pathologically and biologically. While the diagnosis of breast cancer in its pre-invasive phase, DCIS, allows the likelihood of cure with effective therapy, issues that surround its pathological heterogeneity are often not fully understood nor recognised. In this paper, the pathology and natural history of breast DCIS are reviewed; with emphasis on pathological classification schemes that attempt to predict recurrent disease or progression to invasive cancer. The potential role of biological markers is also evaluated. Atypical ductal hyperplasia, a lesion that is often difficult to distinguish from low grade DCIS; the significance and definition of microinvasion; and the value of fine needle aspiration cytology in DCIS are discussed. In addition, pathologic-radiologic correlations of local screen-detected cases of breast DCIS are presented. Awareness of the pathological parameters that impact on the biological behaviour of breast DCIS will enable appropriate management strategies; avoiding overtreatment in biologically indolent disease, while optimising adequate therapy for aggressive lesions.