Margin status of breast conserving therapy specimens in ductal carcinoma in situ of the breast detected by microcalcifications: radiological-pathological correlation in specimen slices

Aim:

Positive margins in breast conserving therapy (BCT) specimens are a risk factor for local recurrence in ductal carcinoma in situ (DCIS). As DCIS often bears microcalcifications, intraoperative specimen or slice radiograms are widely used to guide BCT surgery. However, as in some DCIS parts microcalcifications may be absent, margin widths based on microcalcifications alone may differ from final histological DCIS margin status. Our aim was to compare radiological margin widths measured on slice radiograms with respective histological DCIS margins of BCT specimens.

Methods:

90 parenchymal margins of 45 slices from 17 BCT specimens containing both microcalcifications and DCIS were investigated. Margin width of microcalcifications in slice radiograms was measured by two radiologists and compared with histopathological DCIS margins in whole slice mega- or jumbo-slides.

Results:

There was a moderate positive overall correlation between radiogram based and histological margin widths (R = 0.67, p < 0.001). Radiological margin width compared to histological DCIS margin status was overestimated (> 2 mm) in 72 (80%) and underestimated (> 2 mm) in 6 (7%) margins. Discrepancies between radiological and pathological margins of ≤2 mm, 3 – 5 mm, 6 – 10 mm, 11 – 20 mm and > 20 mm were found in 12 (13%), 15 (17%), 13 (14%), 22 (24%) and 28 margins (31%), respectively.

Conclusions:

DCIS margin widths in BCT specimens tend to be considerably overestimated by radiological microcalcification based margin measurement. This should be considered in preoperative resection volume planning.