Detection of Ductal Carcinoma In Situ by Ultrasound and Mammography: Size-dependent Inaccuracy.

BACKGROUND: Retrospective analysis of breast cancer imaging methods is a common tool for evaluating the effectiveness of ultrasound and mammography regarding ductal carcinoma in situ (DCIS). No large number subpopulation of pure DCIS has been reported. It is however known that mammography and ultrasound underestimate tumor dimension with increasing tumor size. We aimed to quantify this discrepancy. MATERIALS AND METHODS: This retrospective analysis reviewed the ultrasound and mammography data from 173 patients with DCIS at the University of Cologne - Department of Gynecology and Obstetrics between the years 2007 and 2010. Of these 173 patients, 34 fulfilled the DCIS analysis requirements and were evaluated in this study. RESULTS: Overall, ultrasound underestimated tumor size 79.4% of the time, while overestimating only 20.6% of the time. Mammography underestimated tumor size in 50%, overestimated in 38.2%, correctly estimating in 11.8%. Over and underestimation distributions differed drastically above and a cut-off point of ≤2 cm actual tumor size, with a significant shift toward severe underestimation by both methods above a tumor size of 2 cm. DCIS misestimation was defined as the absolute value of the difference between actual tumor size and pre-surgical measurement by an imaging method. Mean DCIS size misestimation (actual tumor size ≤2 cm) was 3 mm for ultrasound and 6.2 mm for mammography. CONCLUSION: We support previous findings that ultrasound and mammography lose accuracy with increasing tumor size. Nonetheless, ultrasound may be more useful in estimation of DCIS size for tumors ≤2 cm than previously expected.