Proliferative assessment of craniopharyngioma and epidermoid by nucleolar organizer region staining

The histologic distinction between craniopharyngioma and epidermoid is equivocal. Eight craniopharyngiomas and ten epidermoids (including three dermoids) as well as nine rat (Wistar) abdominal skins that acted as control were investigated by a silver colloid method for nucleolar organizer regions (Ag-NORs). The mean number of Ag-NORs in at least 200 cells of both basal (columnar) epithelial cells and suprabasal (prickle) cells was evaluated. It was found that the mean number of Ag-NORs in basal cells of epidermoid and rat skin was significantly greater than that in suprabasal cells (P < 0.001 in nine of ten epidermoids and in all rat skins). On the other hand, of eight craniopharyngiomas, the mean Ag-NOR number in basal cells was not significantly different from that in suprabasal cells in five cases, and, further, the former was significantly smaller than the latter in the other three cases (P < 0.01 in two and P < 0.05 in one). These findings suggest that a stepwise maturation of the epithelial cells like that in mammalian skin epidermis exists in epidermoids but not in craniopharyngiomas. In craniopharyngiomas, the maturation of the epithelial cells seems to be considerably limited or lost from the aspect of proliferative potential as assessed by Ag-NOR score, which indicates neoplastic growth of craniopharyngiomas. Ag-NOR staining may thus be a useful method to distinguish craniopharyngioma from epidermoid.