Part II. Medical Imaging of Ductal
Carcinoma In Situ ~J~ efore screening mammography, the clinical presentation of ductal carcinoma in situ (DCIS) included a palpable mass, nipple discharge or the setting of Paget's disease. Furthermore, DCIS was frequently extensively distributed throughout the breast and was therefore treated with mastectomy. Currently, DCIS is usually seen with abnormal microcalcifications on a screening mammogram and can more frequently be treated with a breast-conserving approach.
DCIS is a heterogeneous disease with varied radiographic appearances. Therefore, the breast radiologist has many roles related to DCIS---early detection, preoperative diagnosis with core biopsy, determination of the extent of disease, intraoperative and postoperative assessment of completeness of excision and, finally, early detection of recurrence. The National Surgical Adjuvant Breast Project (NSABP) B-17 trial, l a randomized clinical trial in which local excision alone was compared with local excision followed by radiotherapy, showed that after breast-conserving surgery without radiation, in 26.8% of patients, a local recurrence developed, recurred and half of the local recurrences were invasive cancer. The possibility that short-term recurrences are caused by the presence of residual disease after initial local excision has heightened emphasis on the need for accurate preoperative imaging to help guide the surgical decision-making process, as well as accurate intraoperative and postoperative imaging to ensure that the entire lesion has been removed.
Mammography
Mammography is the most important imaging modality for the detection of DCIS, for assessment of the extent of disease, and to facilitate radiographic-guided biopsies to confirm the diagnosis of intraductal carcinoma. The mammographic appearance of DCIS is often varied, which reflects the biological heterogeneity of DCIS; however, the presence of a cluster of microcalcifications is the most common presentation. In a published report by Tabar et al 2 on 207 cases of DCIS, mammographic abnormalities were seen in 198 cases (95%). Mammographic findings included the presence of microcalcifications (76%), asymmetric density (10%), the presence of a dominant mass (8%), and abnormal galactograms in patients with nipple discharge (6%). 2