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Abstract：
Ameloblastoma is a locally aggressive tumor derived from the odontogenic epithelium of the developing tooth germ. It is rarely reported in experimental Sprague-Dawley (SD) rats. In this 90-day percutaneous repeated-dose toxicity study, mandibular nodules were observed from day 56 to 90. Upon necropsy, a well-demarcated nodule, approximately 1.2×1.0×1.0 cm, was found attached to the mandibular bone, alongside the unerupted left incisor. Histopathologically, the epithelial cells formed islands, nests, or anastomosing strands. The epithelial islands were surrounded by a peripheral layer of tall columnar cells with antibasilar nuclei arranged in a palisading pattern. Several mitotic cells were observed. Some epithelial islands displayed cystic degenerative changes and squamous metaplasia. Necrotic tissue with inflammatory cell infiltration was observed at the tumor margins. Immunohistochemically, the neoplastic epithelial islands and mesenchymal components exhibited positivity for pan-cytokeratin and vimentin, respectively. Based on these features, the case was diagnosed as follicular ameloblastoma in an SD rat.
摘要：
成釉细胞瘤是一种局部侵袭性肿瘤，源自发育中的牙胚的牙源性上皮。在实验性Sprague-Dawley（SD）大鼠中很少报道。在这项为期90天的经皮重复剂量毒性研究中，从第56天到第90天观察下颌结节。尸检时,一个界限分明的结节，约1.2×1.0×1.0厘米，被发现附着在下颌骨上,在未开的左门牙旁边。组织病理学,上皮细胞形成岛屿，巢,或吻合股。上皮岛被高柱状细胞的外围层包围，这些细胞的反基底核呈栅栏状排列。观察到几个有丝分裂细胞。一些上皮岛显示囊性退行性改变和鳞状化生。在肿瘤边缘观察到有炎性细胞浸润的坏死组织。免疫组织化学，肿瘤上皮岛和间质成分对泛细胞角蛋白和波形蛋白呈阳性，分别。基于这些特征,该病例在SD大鼠中被诊断为滤泡性成釉细胞瘤。
