Effect of stereotactic core needle biopsy on pathologic measurement of tumor size of T1 invasive breast carcinomas presenting as mammographic masses.

Background: Stereotactic core needle biopsy (SCNB) may change the size of the tumor defined pathologically at excision. This may alter tumor stage and affect recommendations for adjuvant systemic therapy. This study evaluated the effect of SCNB on assessment of pathologic tumor size and staging for invasive breast carcinomas presenting as mammographic masses.

Methods: The authors reviewed the mammographic and pathologic size of 138 mammographically detected invasive carcinomas manifested as a measurable mass lesion on mammography and as a 20 mm or smaller lesion on pathologic evaluation. Group A included 61 patients with SCNB before surgical excision and the Group B (the control group) included 77 patients who had surgical excision without SCNB. The size of the mammographic central mass was compared with the pathologic tumor size. The difference between the mammographic and pathologic size was determined and the findings in Group A and B were compared by the Mann-Whitney U test.

Results: The mean mammographic size was 12.2 and 11.83 mm and the mean pathologic size was 9.85 and 9.87 mm for Groups A and B, respectively. The mean difference between mammographic and pathologic size in Groups A and B was 2.3 mm and 1.96 mm, respectively (P = not significant).

Conclusions: For soft tissue masses, the difference between mammographic size and pathologic size of invasive carcinoma at excision does not appear to be affected by the use of SCNB. Except in the circumstance of complete removal of the cancer by SCNB, the pathologic size and stage of the excised tumor after SCNB is not altered significantly by SCNB.