Classic Adamantinoma, Differentiated Adamantinoma and OsteofibrousDysplasia of Long Bones

Overview

Background.
Just for over 100 years, adamantinoma has been recognized as a primary enigmatic bone tumour withepithelial characteristics and predominantly involving the tibia. Several similarities between osteofibrous dysplasiahas been recognised, differentiated adamantinoma and classic adamantinoma. The purpose of this study was tocompare these lesions and to define their histogenesis and mutual relations.Methods and Results. Comparison of the clinical, radiologic, histological, immunohistochemical and electronmicroscopic findings was carried out on 6 cases of classic adamantinoma, 2 cases of differentiated adamantinomaand 2 cases of osteofibrous dysplasia. This study confirmed the epithelial nature of long bone classical anddifferentiated adamantinomas irrespective of their wide-ranging morphologic pattern that can mimic tumours ofvarious origins. Both types of adamantinoma were positive for cytokeratins in coexpression with vimentin. Theepithelial component of the differentiated adamantinoma was much smaller than in classic adamantinoma and waspresent in scattered islands or single cells distributed within fibrovascular stoma. In one case the scattered epithelialcells had abundant eosinophilic cytoplasm and they resembled rhabdoid elements.On the basis of distinct histologicalpattern, a new variant of differentiated adamantinoma was described – a rhabdoid variant. In our cases of osteofibrousdysplasia occurring in two children with deformity of the tibia no epithelial cells were identified by the imunohistochemicalmethods. The lesions were composed of variably shaped spicules of woven and lamellar bone separatedby a fibrovascular stroma. The woven bone spicules were surrounded by a uniform rim of plump osteoblasts. Thelesion exhibited a zonal phenomenon with maturation of woven bone to bone with a lamellar configuration at theperiphery of the lesion. The similar zonal phenomenon was also observed in the cases of differentiated adamantinoma.Conclusions. On the basis of the clinical, histological, immunohistochemical and electron-microscopical studies,a common histogenesis for classic adamantinoma, differentiated adamantinoma and osteofibrous dysplasia seemslikely. The epithelial cell components of these lesions exhibit similar cytokeratin immunoprofiles and ultrastructuralfeatures. However, the prognosis for classic adamantinoma is much less favorable than that for cases of osteofibrousdysplasia and differentiated adamantinoma.

Key words:
classic adamantinoma, differentiated adamantinoma, osteofibrous dysplasia, histopathology,immunohistochemistry, electron microscopy, histogenesis.