Margin status in calcifying ductal carcinoma in situ components of invasive breast cancer: radiological-pathological correlation in slice radiograms of breast conserving therapy specimens

Aim:

Positive or narrow margins in breast conserving therapy (BCT) specimens are a risk factor for local recurrence in invasive breast cancer with extratumoral ductal in situ carcinoma (DCIS). Intraoperative specimen radiograms are widely used to assure margins free of suspicious microcalcifications. Since not all DCIS bear microcalcifications, final histopathological margin status may differ from radiological margin status. Our aim was to compare radiological and pathological DCIS margin status in slice radiograms of BCT specimens.

Methods:

190 parenchymal margins of 95 slices from 20 BCT specimens containing both microcalcifications and DCIS were selected. Margin width of microcalcifications in the slice radiogram was measured by two radiologists and compared with final histopathological DCIS margins in whole slice mega- or jumbo-slides.

Results:

Median margin width was 14 ± 16.58 mm for microcalcifications and 15 ± 12.26 mm for DCIS. There was a low positive correlation between margin widths of microcalcifications and of DCIS (R = 0.275).

Discrepancies between radiological and pathological margins of ≤2 mm, 3 – 5 mm, 6 – 10 mm, 11 – 20 mm and > 20 mm were found in 29 (15%), 35 (18%), 40 (21%), 49 (26%) and 37 margins (19%), respectively. Radiological margin width compared to final DCIS margin status was underestimated (> 2 mm) in 64 (34%) and overestimated (> 2 mm) in 97 (51%) margins due to DCIS units not bearing microcalcifications.

Conclusions:

Radiological margins measured for microcalcifications tend to overestimate DCIS margin status due to non-calcifying DCIS parts. For complete resection of DCIS components of invasive breast cancer, margins should exceed the area of suspicious microcalcifications.