Chordoma in the tail of a ferret.

A chordoma is an uncommon tumor that originates from the remnants of the notochord and most commonly involves the cranial and caudal regions of the axial skeleton. Chordoma has been described in laboratory animals such as dogs, rats, minks, and ferrets. This report describes a case of a chordoma in the tail of a ferret. Grossly, a grayish-white, expansile, subcutaneous soft-tissue mass was observed in the tail. Histopathologically, the mass was a loosely placed, nodular, unencapsulated neoplasm within the dermis. In the mass, tumor lobules were intermingled with fibrous tissues. Fibrous tissues contained abundant extracellular basophilic material that was consistent with mucin. The tumor was composed of a close pack of adipocyte-like vacuolated cells (physaliferous cells). The cells were centrally or eccentrically located round nuclei and eosinophilic cytoplasm with large vacuoles. Immunohistologically, neoplastic cells were positive for vimentin and S-100 protein. Based on histopathologic findings and special staining characteristics, this case was diagnosed as chordoma.