Open breast biopsy is considered to be the most reliable method for the diagnosis of breast cancer in patients with palpable masses. Rarely, after a breast biopsy has been reported to be benign, cancer will be identified at the site of the biopsy. Eight patients were reviewed in whom breast cancer was demonstrated at the site of a previously negative biopsy at intervals ranging between 4 months and 3 years after the original, negative biopsy. Several possible explanations exist to account for this occurrence. The surgeon must be aware that the presence of a mass at the site of prior breast biopsy may be an indication for repeat excision.