Histochemical and immunohistochemical characterization of chordoma in ferrets

Abstract

Chordomas of the tip of the tail in 6 ferrets were examined using histopathological, histochemical and immunohistochemical procedures. Histopathologically, round neoplastic cells containing numerous cytoplasmic vacuoles of varying sizes, categorized as "physaliphorous cells", were observed in the amorphous eosinophilic or pale basophilic myxoid stroma. Physaliphorous cells were arranged in lobules and in a "chordoid" or "cobblestone" manner. The neoplasms were diagnosed as benign chordoma without local invasion and metastasis. Histochemically, the cytoplasm of small neoplastic cells was positive for periodic acid-Schiff stain and alcian blue (AB) pH 2.5 and pH 1.0 stains, but negative for hyaluronidase digestion-AB pH 2.5 stain. All neoplastic cells were strongly stained with colloidal ion, negative for high iron diamine AB pH 2.5 and toluidine blue pH 2.5 stains, and positive for Mayer's mucicarmine stain. Immunohistochemistry using antibodies directed against low-molecular-weight cytokeratins (CK18, CK19 and CK20), vimentin and mucin core protein (MUC5AC) revealed that neoplastic cells had both epithelial and mesenchymal elements. The expression of low-molecular-weight cytokeratins suggests that neoplastic cells acquired the properties of glandular epithelial cells and produced epithelial mucus. Furthermore, the expression of cytokeratins, vimentin, S100 protein, brachyury and epithelial membrane antigen indicates that the neoplasms were equivalent to the classic type of human chordoma. Therefore, immunohistochemistry using these antibodies can be useful for the characterization of ferret chordoma.

Fig. 1.

Neoplastic cells containing multiple cytoplasmic vacuoles of varying sizes (arrows) arranged in lobules, with abundant extracellular myxoid stroma (physaliphorous cells) (case No. 1). HE. Bar=200 µm.

Fig. 2.

Cells with an entire vacuolated cytoplasm and with the nucleus located at the margin of the cytoplasm were categorized as vacuolated cells (case No. 1). HE. Bar=200 µm.

Fig. 3.

Neoplastic cells with foam in the cytoplasm (arrow) and extracellular matrix were strongly stained by the CI stain (case No. 1). Bar=125 µm.

Fig. 4.

Neoplastic cells with foam in the cytoplasm (arrows) were strongly stained by the mucicarmine stain (case No. 1). Bar=125 µm.

Fig. 5.

Neoplastic cells stained strongly by the anti-CK AE1/AE3 antibody (arrow). CK AE1/AE3 immunoreactivity is distributed widely throughout the cytoplasm (case No.1). Bar=125 µµm.

Fig. 6.

Most of the neoplastic cells were strongly stained by the anti-CK 19 antibody (arrows) (case No.1). Bar=125 µm.

Fig. 7.

MUC5AC expressed on the surface of cell membranes and in the cytoplasm of neoplastic cells (arrow) (case No.1). Bar=125 µm.

Fig. 8.

The nuclei of most neoplastic cells in the chordoma were stained by the anti-brachyury antibody (arrow), which is diagnostic for human chordomas (case No.1). Bar=125 µm.