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