title: Atypical canine mammary adenoma characterized by cystic ducts comprising a single layer of basaloid cells with myoepithelial differentiation.
abstract: This report describes an atypical mammary adenoma with a rare histological feature characterized by proliferating single-layered cystic ducts composed of basaloid cells with frequent myoepithelial differentiation. A 9-year-old, intact female Miniature Pinscher dog had mammary tumors on the thorax. Histologically, one of tumors comprised the proliferation of two types of tubular structures; the single-layered cystic ducts lined by flattened cells and double-layered tubules with luminal cells and outer spindle cells. The former ducts were predominant in the tumor and contained pale basophilic mucus, which was Alcian blue (pH 2.5)-positive, but periodic acid Schiff-negative. Immunohistochemical staining indicated that the cells lining single-layered cystic ducts were negative for the luminal epithelial marker, cytokeratin (CK) CAM5.2, but were constantly positive for basal cell markers CK14 and p63 and frequently positive for SMA. Electron microscopy revealed fine, parallel myofilaments within these single-layered neoplastic cells. These histological and immunohistological examinations suggested that the origin of the tumor was bipotential mammary progenitor cells with predominant differentiation into the myoepithelial progenitor linage.
authors.affiliation: Research Institute of Biosciences, Azabu University, 1-17-71 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5201, Japan.
authors.forename: Kyohei
authors.initials: K
authors.lastname: Yasuno
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Kobayashi
authors.forename: Takayuki
authors.initials: T
authors.lastname: Mineshige
authors.forename: Go
authors.initials: G
authors.lastname: Sugahara
authors.forename: Masahiko
authors.initials: M
authors.lastname: Nagata
authors.forename: Junichi
authors.initials: J
authors.lastname: Kamiie
authors.forename: Kinji
authors.initials: K
authors.lastname: Shirota
mesh_terms: D000236:Adenoma / Q000473:pathology / Q000662:veterinary*; D000423:Alcian Blue; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D001943:Breast Neoplasms / Q000473:pathology / Q000662:veterinary*; D002454:Cell Differentiation / Q000502:physiology*; D049109:Cell Proliferation; D003549:Cystic Duct / Q000473:pathology*; D004283:Dog Diseases / Q000473:pathology*; D004285:Dogs; D004847:Epithelial Cells / Q000502:physiology*; D005260:Female; D007150:Immunohistochemistry / Q000662:veterinary; D007633:Keratins / Q000378:metabolism; D008854:Microscopy, Electron; D009210:Myofibrils / Q000648:ultrastructure
chemical_list: D015415:Biomarkers; C400901:CAM 5.2 antigen; D007633:Keratins; D000423:Alcian Blue