title: Pulmonary microcystic hamartoma in an adult dog.
abstract: Microcystic hamartoma was detected as a tumorlike mass in the left caudal lung lobe of a 12-year-old mixed-breed dog. Histologically, the mass was characterized by microcysts of various sizes that mimicked alveoli and were surrounded by thin fibrous septal tissue. However, unlike the adjacent lung parenchyma, bronchial or bronchiolar trees were absent, and the septal vascular channels were extremely underdeveloped. Immunohistochemically, the cells lining the microcysts were consistently positive for cytokeratin but not for vimentin, whereas the septal fibroblast-like cells were negative for cytokeratin and positive for vimentin. Electron microscopy confirmed that the microcysts were lined with a layer of type I and type II mature pneumocytes. This is the first description of the detailed morphologic features of microcystic hamartoma.
authors.affiliation: Department of Veterinary Pathology, Nippon Veterinary and Animal Science University, Tokyo, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Takahashi
authors.forename: K
authors.initials: K
authors.lastname: Maeda
authors.forename: S
authors.initials: S
authors.lastname: Nakamura
authors.forename: M
authors.initials: M
authors.lastname: Fujita
authors.forename: H
authors.initials: H
authors.lastname: Orima
authors.forename: M
authors.initials: M
authors.lastname: Tagawa
authors.forename: M
authors.initials: M
authors.lastname: Kuwahara
authors.forename: N
authors.initials: N
authors.lastname: Nakashima
authors.forename: K
authors.initials: K
authors.lastname: Maita
mesh_terms: D000818:Animals; D004283:Dog Diseases / Q000473:pathology* / Q000601:surgery; D004285:Dogs; D006222:Hamartoma / Q000473:pathology / Q000601:surgery / Q000662:veterinary*; D008168:Lung / Q000000981:diagnostic imaging / Q000473:pathology; D008171:Lung Diseases / Q000473:pathology / Q000601:surgery / Q000662:veterinary*; D008854:Microscopy, Electron / Q000662:veterinary; D014463:Ultrasonography