OBJECTIVE: To characterize the incidence and primary origin of metastatic carcinomas to the breast diagnosed by fine needle aspiration (FNA) and core needle biopsy at our institution, to describe their clinicopathologic and cytomorphologic features, and to determine the efficacy of FNA and core needle biopsy with rapid on-site evaluation (ROSE) imprint cytology in this setting. STUDY DESIGN: We analyzed 22,625 FNAs and/or core needle biopsies examined at our institution during a 15.2-year period. RESULTS: There were only 9 patients with metastatic carcinomas to the breast, entailing 0.04% of all breast FNA and core needle biopsies and 1.9% of all breast malignancies. Metastatic lung carcinoma was most common (44%), followed by gynecologic cancers (22%). Our remaining 3 metastases were a urothelial carcinoma, melanoma, and colonic adenocarcinoma. ROSE was utilized in 56% of cases, with resulting imprint cytologies correlating with final histologic diagnoses in all cases. ROSE facilitated the use of smaller core needles. CONCLUSION: Metastatic carcinomas to the breast are exceedingly rare at our institution. FNA and core needle biopsy in conjunction with ROSE were effective diagnostic modalities. ROSE with imprint cytology may enhance the diagnostic accuracy of breast core needle biopsy while lowering the associated morbidity, thereby precluding more invasive procedures in the evaluation of metastatic lesions. © Science Printers and Publishers, Inc.