Fine-needle aspiration biopsy (FNAB) of the breast has been widely used in many centers worldwide for the initial management of patients with breast lumps. However, little has been written on the morphologic changes secondary to this commonly applied procedure. Thus we performed a retrospective study on 184 consecutive breast-excision specimens with a history of FNAB. Seventeen cases (9.2%) showed changes definitely attributable to the FNAB procedure, including three cases of near total destruction of the lesion as a result of hemorrhage (one case) or infarction (two cases), focal hemosiderin deposition (seven cases), hemorrhage with organization at the periphery (six cases), and a case of ductal papilloma showing a previously undescribed occurrence of benign epithelial implantation. The latter exhibited alarming histologic features simulating invasive carcinoma by virtue of the presence of small narrow tubules with mild cellular atypia haphazardly distributed in the fibrogranulation tissue around the papilloma; the tubules were confirmed to be benign by the presence of muscle-specific actin-positive myoepithelial cells. Other changes were possibly attributable to the FNAB procedure, including linear necrosis in the peripheral portion of the tumor (six cases), intraluminal hemorrhage in fibroadenoma (five cases), and multicentric hemorrhage in the mucinous carcinomas (four cases). We conclude that the rare occurrence of extensive tissue necrosis after FNAB can pose great difficulties in definitive diagnosis of the lesion in the subsequent excision specimen. Other changes are relatively minor, but the occurrence of benign implantation after FNAB may lead to an erroneous diagnosis of invasive carcinoma.