Diagnosis of Trichoepithelioma in a Tree Shrew and Observation of Cell Biological Characteristics

Objective To observe the primary tumor of tree shrews and to provide a basis for studying the pathogenesis and prevention of trichoepithelioma.Methods A tumor was discovered in the chest and abdomen of a tree shrew during natural cultivation. The tree shrew was anesthetized, and the tumor was surgically removed. Hematoxylin and eosin (HE) staining and immunohistochemical staining were performed on the tumor tissue after paraffin section, and the tumor cells were isolated and cultured by passage. The isolated tumor cells were subcutaneously injected into healthy tree shrews and nude mice. The tumorigenesis of tumor cells in vivo was observed once a day, with nude mice continuously observed for 2 months and tree shrews observed for more than 6 months.Results HE staining showed that the basal cells in the dermis were arranged as a whole, like a string of petals, forming nests and stripe-like structures with clear boundaries. The observation results after magnification revealed that the tumor cells were arranged in a pallisade-like and basal pattern, with deep nuclear staining and minimal cytoplasmic. Immunohistochemical staining showed the high expression of CK protein and low proportion expression of ki-67 protein in tumor cells, as well as the high expression of vimentin and low expressions of Bcl2 and CD10 in tumor cell mesenchyme. The isolated tumor cells grew well in DMEM medium containing 10% fetal bovine serum and could be cultured by passage, but no tumor formation was observed in healthy tree shrews and nude mice inoculated with tumor cells.Conclusion Combined with the location of the tumor, overall morphology, HE staining, and immunohistochemical results, the thoracoabdominal mass of the tree shrew was diagnosed as a trichoepithelioma.