Case report 235. Ewing-like adamantinoma of the left radial head and neck.

Skeletal adamantinoma is a rare malignant bone tumor with a poorly understood histogenesis. The lesion is easily recognized by a distinctive microscopic pattern of anastomosing trabeculae of epithelial-like cells in a fibrous stroma. Ultrastructural evidence has been presented to support an origin from two widely-divergent cell types: an epithelial cell with squamous characteristics [12, 15] and a mesenchymal cell with endothelial features [5, 9]. An addition to the histogenetic controversy has been the recent description of a bone neoplasm with an adamantinoma-like growth pattern which proved both by subsequent histological evolution and ultrastructure, to have features of Ewing tumor [10]. The authors report a further example of this entity and suggest that it may be sufficiently distinctive within the adamantinoma group to merit the term Ewing-like adamantinoma. Consonant with increasing evidence supporting the concept of tumor "metaplasia" that transcends traditional concepts of epithelial-mesenchymal immutability, the authors propose that all adamantinomas arise from a common stem cell.