title: A spontaneous epithelial-myoepithelial carcinoma of the submandibular gland in a sprague-dawley rat.
abstract: The present report describes a rare case of spontaneous tumor of the salivary gland in a male Sprague-Dawley rat. The clinically confirmed mass rapidly developed in the cervical region between 19 and 21 weeks of age, and the animal was subsequently euthanized. At necropsy, a well-circumscribed nodule approximately 7 × 6 cm in diameter was found at the site of the salivary gland. The cut surface of the nodule was lobulated and soft and had a pinkish tan fish-flesh appearance. One large cyst (approximately 3 × 2 cm in size) containing reddish fluid was also present in the nodule. Histopathologically, the tumor, with a partially lobulated structure, was surrounded by a thin fibrous capsule. The majority of tumor cells formed a diffuse solid sheet structure that mainly consisted of small ovoid or spindle-shaped cells. In the tumor periphery, some cells were arranged in nest-like structures. Small duct-like structures lined with a monolayer of cuboidal epithelial cells resembling an intercalated duct or large polygonal clear cells with a myoepithelial component were also observed. Mitotic figures and necrotic foci were frequently observed in solid areas. Immunohistochemically, the tumor cells were positive for cytokeratin, epithelial membrane antigen, vimentin, p63, α-smooth muscle actin and calponin. The cells were negative for calcitonin, synaptophysin and chromogranin A. On the basis of these findings, the tumor was diagnosed as an epithelial-myoepithelial carcinoma originating from the luminal epithelial cells and myoepithelial cells in the submandibular gland.
authors.affiliation: Department of Pathology, Chemon Co., Ltd., 240 Nampyeongro, Yangji-Myeon, Cheoin-Gu, Yongin-Si, Gyeonggi-Do 449-826, Republic of Korea.
authors.forename: Yinghua
authors.initials: Y
authors.lastname: Li
authors.forename: Hak-Soo
authors.initials: HS
authors.lastname: Kim
authors.forename: Min-Soo
authors.initials: MS
authors.lastname: Kang
authors.forename: Seo-Ho
authors.initials: SH
authors.lastname: Shin
authors.forename: Kyo-Hwan
authors.initials: KH
authors.lastname: Koo
authors.forename: Chul-Min
authors.initials: CM
authors.lastname: Kim
authors.forename: Kap-Ho
authors.initials: KH
authors.lastname: Kim
authors.forename: Charles
authors.initials: C
authors.lastname: Peck
authors.forename: Han-Ik
authors.initials: HI
authors.lastname: Bae
authors.forename: Ji Yun
authors.initials: JY
authors.lastname: Jeong
authors.forename: Jin Seok
authors.initials: JS
authors.lastname: Kang
authors.forename: Boo-Hyon
authors.initials: BH
authors.lastname: Kang
keywords: Sprague-Dawley rat; epithelial-myoepithelial carcinoma; immunohistochemical features; submandibular gland