Comparative immunohistochemical assessment of craniopharyngioma and related lesions

Craniopharyngiomas (CP), Rathke's cleft cysts (RCC), and sellar xanthogranulomas (XG) are closely related lesions. As expression of cytokeratins 8 (CK8) and 20 (CK20) was reported in RCC but not in CP, the present study investigates the reproducibility of immunohistochemical distinction between CP and RCC, attempting to identify the relationship of XG to these lesions. A comparative study of 55 patient specimens (25 CP, 28 RCC, and 2 XG) was analyzed for the histological features of xanthomatous changes and squamous metaplasia, and expression of CK8 and CK20. In the 25 CP cases, xanthomatous changes were seen in 5 (20%), with CK8 reactivity demonstrated in all 25 cases. A prominent xanthomatous component was identified in 13 of 28 RCC (46%), and squamous metaplasia was seen in 11 (39%), 9 of which also contained xanthomatous features. CK8 reactivity was demonstrated in all 28 RCC cases, whereas CK20 was seen only in 9 cases (32%). Of the two cases diagnosed as XG, none contained epithelium, and immunohistochemistry for cytokeratins was not observed. Overall, differential expression of cytokeratins cannot reliably distinguish CP from RCC. Furthermore, expression of CK20 in RCC is generally seen within a background of prominent squamous metaplasia and reactive xanthomatous changes.