Columnar Cell Lesions of the BreastSchnitt, Stuart J.*; Vincent-Salomon, Anne†Advances in Anatomic Pathology: May 2003 - Volume 10 - Issue 3 - pp 113-124 Review Articles Abstract Author Information Columnar cell lesions of the breast represent a spectrum of lesions which have in common the presence of columnar epithelial cells lining variably dilated terminal duct lobular units, ranging from those that show little or no cytologic or architectural atypia to those that show sufficient cytologic and architectural features to warrant a diagnosis of atypical ductal hyperplasia or ductal carcinoma in situ. Recent studies have begun to provide insights into the biological nature and clinical significance of these lesions. In this article, we review the current state of knowledge and propose a simplified scheme for their classification. Lesions characterized by the presence of columnar epithelial cells lining the terminal duct lobular units (TDLUs) of the breast have long been recognized by pathologists, and have been described under a variety of different names (1–15). Recently, there has been renewed interest in these lesions because they are being encountered with increasing frequency in breast biopsies performed because of the presence of mammographic microcalcifications (13,14). Unfortunately, the lack of standardized terminology and the paucity of information regarding their clinical significance have created difficulties in both pathologic diagnosis and patient management. The purpose of this article is to review the available literature dealing with columnar cell lesions of the breast to better understand their pathologic features and clinical significance. *Department of Pathology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, U.S.A; and †Service de Pathologie, Institut Curie, Paris, France. Address correspondence and reprint requests to Dr. Stuart J. Schnitt, Department of Pathology, Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Boston, MA 02215. © 2003 Lippincott Williams & Wilkins, Inc.