Different keratin profiles in craniopharyngioma subtypes and ameloblastomas

Craniopharyngiomas are generally considered to arise from the remnants of Rathke's pouch or a misplaced enamel organ. We tried to refine these hypotheses, comparing the subtypes of craniopharyngioma with Rathke's cleft cyst, a known Rathke's pouch derivative, and with ameloblastoma, an enamel organ derivative. Nineteen craniopharyngiomas (14 adamantinomatous and 5 papillary type tumors) and 17 ameloblastomas were immunostained for cytokeratin (CK) 7, CK 8, CK 14, and human hair keratin (HHK). All cases of adamantinomatous craniopharyngioma were CK 7(+)/CK 8(+)/CK 14(+). Two cases (40%) of papillary craniopharyngioma were CK 7(+)/CK 8(+)/CK 14(+), whereas the remaining three cases (60%) were CK 7(+)/CK 8(-)/CK14(+). Fifteen cases (88%) of ameloblastoma were CK 7(-)/CK 8(+)/CK 14(+). Only the shadow cells present in adamantinomatous craniopharyngiomas were positive for HHK, which may indicate their follicular differentiation. In Rathke's cleft cyst, ciliated cuboidal cells were CK 7(+)/CK 8(+)/CK 14(-) and metaplastic squamous cells were CK 7(+)/CK 8(-)/CK 14(+). These findings suggest that both subtypes of craniopharyngioma may differ from ameloblastoma in histogenesis, although cytokeratin expression patterns may change during tumor development. Adamantinomatous craniopharyngioma may be related to a heterotopic ectodermal tissue which can differentiate into hair follicles, while papillary craniopharyngioma may arise from Rathke's cleft cyst.