Measuring Invasive Breast Carcinoma on Core Biopsy-Is It Necessary? An Analysis of Ultrasound, Mammotome, and Magnetic Resonance Imaging-Guided Core Biopsies

Context.-Pathologic tumor size is significant in the treatment of breast carcinoma and is routinely measured on excision. Objective.-To analyze the need for measuring size of invasive mammary carcinoma on biopsy. Design.-Nine hundred twenty-two cases of invasive carcinoma whose size was measured (greatest linear measurement) on biopsy and excision was correlated, including imaging when available (110 cases). Results.-Patient mean age was 62 years. Most (90%; 830 of 922) carcinomas were ductal and sampled by ultrasound and graded as follows: well, 13% (113 of 922); moderately, 58% (532 of 922), and poorly differentiated, 28% (258 of 922); 19 microinvasive not graded. Tumor mean size was 7.5 mm on biopsy and 14.4 mm on excision. Biopsy modality was as follows: ultrasound, 7.8 mm (92%, 844 of 922); mammotome, 3.3 mm (7%, 65 of 922); and magnetic resonance imaging, 5.9 mm (1%, 13 of 922). Size comparison on biopsy versus excision was biopsy > excision: 8% (72 of 922), biopsy = excision: 10% (95 of 922), and biopsy < excision: 82% (755 of 922). Half (36 of 72) of the biopsy > excision tumors were less than 5 mm, 96% (726 of 755) of biopsy < excision tumors were greater than 5 mm, while those equal on both were predominantly (88%, 84 of 95) less than 10 mm, 20% (19 of 95) of which were microinvasive. Stage changed in 600 cases, staging based on excision in 581 (63%), and staging based on biopsy in 19 (2%). Radiologic-pathologic correlation (n = 110) showed perfect concordance in 11 (10%), 83 (75%) were +/- 1 to 2 mm, and 16 (15%) were +/- more than 3 mm. Difference between the biopsy and excision ranged from a lower limit of 1.3 mm for T1a tumors to 18 mm for T2. Conclusions.-While most carcinomas are larger on excision, 18% (167 of 922) are larger or equal on biopsy. Factors predictive of biopsy > excision tumors include stage 1 tumors (P < .001), especially less than 5 mm, and sampled by mammotome. We recommend measuring invasive carcinoma on biopsy and excision.