Extent of ductal carcinoma in situ in breast conserving surgery specimens: correlation between radiographic measurement of microcalcification areas and histological measurement on large format slides

Aim:

Extent is an independent risk factors for local recurrence in ductal in situ carcinoma (DCIS) of the breast. Surgical strategies mainly depend on extent of microcalcifications in mammograms, but as not all ducts containing DCIS bear microcalcifications, the final extent of DCIS may differ from the radiologically suspected volume. Our aim was to analyse the correlation between radiological estimation and pathological extent of DCIS in breast conserving therapy (BCT) specimens.

Methods:

The extent of microcalcifications in 248 slice radiograms of 17 BCT specimens was measured by two radiologists and compared to histological DCIS size in large format slides of whole slices.

Results:

63 BCT specimen slices contained microcalcifications, 69 slices contained DCIS. Positive predictive value for presence of DCIS in slice radiograms containing suspect microcalcifications was 0.74, negative predictive value for absence of DCIS in slice radiograms without microcalcifications was 0.88. While the positive correlation between radiological extent of microcalcification and final pathological extent of DCIS was a moderate (R = 0.52, p < 0.001), slice radiography overestimated DCIS extent in 32% (22/69) and underestimated DCIS extent in 40% (28/69) of slices containing microcalcifications, while deviations of ≤2 mm between microcalcification vs. DCIS extent were found in 28% (19/69 slices). Underestimations resulted from non-calcifying DCIS components, overestimations from calcified benign lesions.

Conclusions:

As DCIS extent was both over- and underestimated radiologically, the extent of microcalcifications alone should not be used as a surrogate for pathological DCIS size in BCT specimens.