A spontaneous basal cell carcinoma with pulmonary metastasis in a 6-week-old SD rat

To our knowledge, this is the first report on basal cell carcinoma with lung metastasis in a rat. A 6-week-old male Sprague-Dawley rat presented ulceration of the oral mucosa with surrounding tumor growth and white nodules in the lung. Microscopically, the mass showed solid, sheet-like growth with a partially lobular pattern and invaded the gingival mucosa, maxilla, and nasal submucosa. The nuclei of tumor cells were round to oval in shape with basophilic cytoplasm and a large number of mitotic figures. The pulmonary nodules were almost identical to the maxillary tumor in histopathological characteristics. Immunohistochemically, tumor cells were positive for cytokeratin, vimentin, PCNA, and p63 and negative for desmin, S-100, and αSMA. Based on these results, we diagnosed the tumor as a maxillary basal cell carcinoma with pulmonary metastasis.