Research ArticlesBasal Cytokeratin Phenotypes of Myoepithelial Cells Indicates the Origin of Ductal Carcinomas In Situ of the BreastChen, Ling MD*; Yin, Xiaona MD†; Lu, Shanshan MD‡; Chen, Guorong MD‡; Dong, Lei MMS‡,§Author Information *Department of Pathology, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Nanjing, Jiangsu †Department of Pathology, Maternity and Child Health Care Hospital, Jiaxing ‡Department of Pathology, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou §Department of Pathology, Fudan University Shanghai Cancer Center, Shanghai, People’s Republic of China Supported by Wenzhou Science and Technology Bureau Program (H20100015). The authors declare no conflict of interest. Reprints: Lei Dong, MMS, Department of Pathology, Fudan University Shanghai Cancer Center, Shanghai 200032, China (e-mail: [email protected]). Received April 13, 2014 Accepted June 24, 2014 Applied Immunohistochemistry & Molecular Morphology: September 2015 - Volume 23 - Issue 8 - p 558-564 doi: 10.1097/PAI.0000000000000123 Buy Metrics Abstract Terminal duct lobular unit (TDLU) is widely accepted as the origin of ductal carcinoma in situ of breast. The differentiation states of myoepithelial cells of breast ductal system hint the development of breast hyperplastic lesions. Basal cytokeratin (CK) phenotypes indicate the differentiation of myoepithelial cells. Using antibodies of CK5/6, CK14, and CK17, this study reports the basal CK phenotypes of myoepithelial cells in 20 foci of normal breast, 20 usual ductal hyperplasias, 36 ductal carcinomas in situ (DCIS), and 28 sclerosing adenosis (SA). The results showed that the positive staining of basal CKs of myoepithelial cells in normal ducts were significantly higher than those in normal lobules. The basal CK expression of myoepithelial cells of DCIS and usual ductal hyperplasia was similar to that of normal duct, whereas that of SA was similar to that of normal lobule. We propose a modified model of TDLU origin of intraductal carcinoma that most of DCIS originate from terminal ducts of TDLU, whereas most SA originate from lobules. Copyright 2015 Wolters Kluwer Health, Inc. All rights reserved.