Reporting the greatest linear extent of ductal carcinoma in situ on needle core biopsy

Ductal carcinoma in situ (DCIS) of the breast is staged as pTis regardless of size; however, extent of DCIS correlates with local recurrence rates and likelihood of close or positive margins. As a result, DCIS extent influences patient management and is an important element in the College of American Pathologists tumor summary checklist for excision specimens. There are no recommendations regarding routine reporting of DCIS extent on needle core biopsy material, and to our knowledge, no systematic studies have evaluated the impact of reporting this in biopsy material. Consecutive cases of DCIS performed or reviewed at our institution were identified by pathology report search over a 7-year period. The greatest linear extent of DCIS on core biopsy was compared with the estimated extent in the excision. Of 241 total cases, there were 157 (65%) cases in which the DCIS extent on biopsy was smaller, 13 (5%) cases in which the sizes were equal, and 70 (29%) cases in which the biopsy size was greater, including 30 (12%) with no residual tumor on excision. Mean extent was greater on excision than on core biopsy (16.0 versus 5.7 mm; P < .0001); however, the opposite was seen when only small tumors (≤ 10 mm final size) were considered (4.5 versus. 3.6 mm; P = .0161). There was strong linear correlation (r = 0.9761; P < .0001) between the size change (excision size minus biopsy size) and final pathologic size. For accurate tumor summary checklist completion, DCIS extent should be reported for needle biopsy material, particularly in the setting of small tumors.