[71] Adamantinoma and Osteofibrous Dysplasia: Diagnostic Application of p63 with Additional Evidence for a Pathophysiologic Relationship

BC Dickson, RS Bell, PC Ferguson, DJC Howarth, KPH Pritzker, JS Wunder, RA Kandel. Mount Sinai Hospital; University of Toronto, Toronto, ON, Canada; Toronto General Hospital, Toronto, ON, Canada; Mount Sinai Hospital, Toronto, ON, Canada

Background: Adamantinoma is a low-grade primary bone neoplasm demonstrating epithelial differentiation. It exhibits some degree of clinical overlap with osteofibrous dysplasia; indeed, a relationship between these lesions has previously been proposed on the basis of cytogenetic similarities and co-expression of keratin. We report the presence of p63 expression in the epithelial component of adamantinomas and sought to determine whether this putative stem cell marker, which is also associated with epithelial-mesenchymal interactions, was also expressed in osteofibrous dysplasia.
Design: We performed a retrospective review of our archives to identify cases of adamantinoma and osteofibrous dysplasia. Five cases of fibrous dysplasia served as controls. H&E stained sections of paraffin embedded tissue were reviewed by light microscopy to confirm the diagnosis. Sections from each case were subsequently stained for p63 using standard immunohistochemical methods.
Results: Nine cases of adamantinoma (six classical, three osteofibrous dysplasia-like) and ten cases of osteofibrous dysplasia were identified. The epithelial component in all cases of adamantinoma was found to express p63. The percentage of epithelial cells expressing this marker appeared greatest in the classical variant. Despite the absence of an epithelial component in osteofibrous dysplasia, rare scattered cells expressing p63 could be identified in eight cases of osteofibrous dysplasia. These cells were scattered amongst the spindle cells and did not appear to be associated with either the vasculature or bone trabeculae. None of five cases of fibrous dysplasia were found to contain p63 expression.
Conclusions: To our knowledge this is the first report of p63 expression in the epithelial cell component of adamantinoma. Moreover, the presence of staining, albeit focal, in osteofibrous dysplasia supports the notion of a relationship between osteofibrous dysplasia and adamantinoma. It remains unclear whether p63 is highlighting a stem cell within osteofibrous dysplasia – a possibility that warrants further consideration.
Category: Bone & Soft Tissue

Tuesday, March 23, 2010 9:30 AM

Poster Session III # 5, Tuesday Morning


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