Spontaneous malignant craniopharyngioma in an aged Wistar rat

Abstract

Craniopharyngiomas are extremely rare epithelial tumors of the sellar region in human beings and domestic and laboratory animals. A craniopharyngioma, 0.6 cm in diameter, was observed grossly in the sellar and parasellar regions of an untreated 23-month-old male Wistar-derived rat sacrificed moribund. The tumor was composed of cords, columns, and nests of neoplastic stratified squamous epithelium with marked hyperkeratosis and parakeratosis. Neoplastic cells formed solid or cystic areas, infiltrating the base of the skull, brain, and pituitary gland. Immunocytochemical evaluation revealed a strong cytoplasmic reaction for pan-cytokeratin in all tumor cells. Malignant craniopharyngioma should be considered a differential diagnosis in the rat when a tumor with stratified squamous epithelial features and a locally aggressive growth pattern is observed in the sellar or suprasellar region.

Keywords: craniopharyngioma; cytokeratin; immunocytochemistry; malignant craniopharyngioma; pituitary tumor; rat.

Fig. 1.

Brain with a tumor in the sellar region (asterisk), indentation, and a solitary focus of invasion in the ventrolateral telencephalon (arrow). Note the distorsion of the median eminence (frontal section). H&E,×20.

Fig. 2.

The tumor is composed of an irregular stratified squamous epithelium with marked hyperkeratosis and parakeratosis, forming solid areas or, predominantly, cysts of varying size filled with desquamated keratin, cellular debris, macrophages, and proteinaceous fluid. H&E, ×160.

Fig. 3.

Mitotic figures are fairly frequent (arrowheads) in the neoplastic stratified squamous epithelium with marked hyperkeratosis and parakeratosis on a delicate fibrovascular stroma. Cysts contain desquamated keratin, cellular debris, and macrophages. Inset: Irregular stratified squamous epithelium with no keratohyaline granules and cyst-like structures filled with desquamated keratin in somehow irregular layers or squames, H&E, ×400.

Fig. 4.

The tumor has deeply infiltrated the base of the skull, destroying most of the sphenoid bone. Tumor cells and desquamated keratin exhibit strong cytoplasmic immunoreactivity for pan-cytokeratin (Lu-5). PAP method, hematoxylin counterstain, Nomarski technique, ×400.

Fig. 5.

The tumor is directly abutting the pituitary gland. Minimal focal infiltration of the pituitary pars distalis is evident (arrows), which shows normal numbers and distributions of GH-immunoreactive cells. PAP method, hematoxylin counterstain, Nomarski technique, ×400.

Fig. 6.

Focus of tumor invasion associated with focal demyelination in the ventrolateral telencephalon from Fig. 1. Cords of neoplastic stratified squamous epithelium with no keratohyaline granules and little or no hyperkeratosis and parakeratosis (arrows) are evident, with marginal hemorrhage and many macrophages, neutrophils and cellular debris within an adjacent cystic focus of demyelination (asterisk). H&E, ×320.