Frequent nuclear expression of β-catenin protein but rare β-catenin mutation in pulmonary sclerosing haemangioma

BACKGROUND: Pulmonary sclerosing haemangioma (PSH) is an uncommon tumour that is composed of glandular/papillary lining cells and polygonal cells. The biological behaviour of this tumour has been investigated; however, the molecular pathogenesis of PSH remains unknown. AIMS: To characterise the role of the Wnt/beta-catenin pathway in the genesis of PSH. METHODS: 37 PSH samples were investigated immunohistochemically for detection of the beta-catenin protein and direct sequencing of exon 3 of the beta-catenin gene. RESULTS: Nuclear expression of beta-catenin was found in the lining component of 23 tumours (62%) and in the polygonal component of 11 tumours (30%). The expression of beta-catenin was stronger in the lining component, but weaker in the polygonal component. Interestingly, all the tumours with expression of beta-catenin in the polygonal component also expressed beta-catenin in the lining component. However, mutation of exon 3 of the beta-catenin gene was detected in only one tumour that expressed nuclear beta-catenin in lining and polygonal components. CONCLUSIONS: The Wnt/beta-catenin pathway is involved in the genesis of PSH, but mutation of exon 3 of the beta-catenin gene rarely contributes to the activation of the Wnt/beta-catenin pathway in PSH.