Immunohistochemical Expression of β-Catenin in Solitary Fibrous Tumors

CONTEXT: Immunohistochemical staining for beta-catenin may be used as an indicator of the integrity of the Wnt signaling and beta-catenin degradation pathways. Among mesenchymal tumors, aberrant nuclear localization of beta-catenin is seen in desmoid-type fibromatoses but has not been described for solitary fibrous tumors that may mimic the former lesions, especially in small biopsy samples. OBJECTIVE: To study the immunohistochemical expression of beta-catenin in solitary fibrous tumors. DESIGN: We performed immunohistochemical staining for beta-catenin in 12 solitary fibrous tumors, one of which showed histologic features of malignancy. RESULTS: All the tumors showed strong and diffuse reactivity for beta-catenin. Four tumors (33%) showed nuclear staining for beta-catenin, whereas the remaining tumors showed either a membranous or mixed membranous and cytoplasmic pattern of staining. The only histologically malignant tumor of the group showed a mixed membranous and cytoplasmic pattern of staining for beta-catenin. CONCLUSIONS: Immunohistochemical staining for beta-catenin in solitary fibrous tumors does not show a consistent pattern, which may be due to differences in tumorigenesis. Larger studies with clinical follow-up are required for estimating the impact of the variable staining pattern on clinical behavior of these tumors.