[en] Background: Carbon marking of the biopsy site and needle track following stereotactic breast biopsy in nonpalpable mammography-detected lesions provides for safe and accurate localization for subsequent surgical excision. No significant complications of carbon marking have been reported to date. Purpose: To report follow-up imaging findings and histological changes (foreign-body giant-cell reaction) attributable to the use of carbon marking after vacuum breast biopsies. Material and Methods: This was a retrospective study of 130 patients in a mammographic screening program with nonpalpable suspicious breast lesions that were referred for stereotactic directional vacuum-assisted breast biopsy with carbon marking. Histological diagnosis was benign in all cases, but 1-year follow-up mammograms demonstrated suspect findings in four of them. Results: For all four patients, the results of the initial stereotactic vacuum-assisted biopsy were benign, but mammographic follow-up and ultrasound findings revealed suspicious changes that, in all cases, were histologically shown to be foreign-body giant-cell reactions attributable to the use of carbon. Conclusion: In four of 130 lesions (3%) that were carbon marked following stereotactic vacuum-assisted breast biopsy, and in which surgical excision was not required, the mammographic and ultrasound follow-up appearance of the breast simulated malignancy. The abnormality was attributable to the use of carbon, which represents a potential source of misdiagnosis