Osteofibrous Dysplasia-Like Adamantinoma: A Case Report with its Immunohistochemical and Ultrastructural Studies

ABSTRACT

Osteofibrous dysplasia (OFD)-like adamantinoma is a rare skeletal tumor that is characterized by the predominant OFD-like pattern with scattered epithelial nests. Adamantinoma shares clinical features (the majority of lesions in the tibia and the prevalent age group), radiologic findings (radiolucency with sclerotic shadow), and pathologic similarities (particularly the presence of scattered cytokeratin-positive stromal cells) with OFD. We describe a case of OFD-like adamantinoma. Epithelial cell nests express the epithelial membrane antigen, pancytokeratin, CK14, and collagen type IV. Ultrastructurally, the oval to spindle cells in the epithelial foci had abundant tonofilaments, and well-formed desmosomes with dense plaques, of which well preserved desmosomes are demonstrated for the first time in OFD-like adamantinoma. These immunohistochemical and ultrastructural findings further support that the origin of epithelial cells of classic and OFD-like adamantinoma are epithelial cells transformed from fibroblastic cells in the proliferating osteofibrous tissue.