Expression and significance of β-catenin and BRAF V600E in craniopharyngiomas

Abstract

Objective To detect the expression and significance of β-catenin and BRAF V600E in craniopharyngiomas. Methods Craniopharyngioma specimens were collected from 51 patients who underwent surgical operations at Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University from January 2008 to December 2010. HE staining was employed to observe morphological characteristics of different types of craniopharyngiomas, and immunohistochemical staining was used to detect the expression of β-catenin, BRAF V600E and Ki-67. Results In 39 out of 42 (93%) cases of adamantinomatous craniopharyngioma (ACP), β-catenin was positive in the nuclei of whirl-like cell clusters, transitional cells by the ghost cells, and/or sporadic single cells, while papillary craniopharyngioma (PCP) showed β-catenin immunoreactivity merely in the membrane rather than the nucleus. Expression of BRAF V600E was detected in 7 out of 8 cases with PCP and absent in ACP. There were 3 cases with untypical morphology of craniopharyngiomas. Among them, 2 cases showed accumulation of nuclear β-catenin protein and conformed to ACP; and the other 1 was BRAF V600E positive in the ciliate on epithelial surface and classified as Rathke’s cleft cyst with squamous metaplasia. In cases of ACP, Ki-67 was negative in cells with nuclear accumulation of β-catenin. Furthermore, the counts of β-catenin positive cell clusters had no significant difference between specimens collected from two operations performed in 8 patients with recurrent ACPs(P<0.05). Conclusion The proteins of β-catenin and BRAF V600E are two specific markers for ACP and PCP, respectively, which may be helpful in classification and differential diagnosis of craniopharyngiomas with untypical morphology. Key words: Craniopharyngioma; Pathology; Dignosis; Wnt signaling pathway; BRAF V600E