DISTRIBUTION OF EXTRACELLULAR-MATRIX COMPONENTS IN ADAMANTINOMA OF LONG BONES SUGGESTS FIBROUS-TO-EPITHELIAL TRANSFORMATION

Adamantinoma of long bones is a rare skeletal tumor of unknown origin with epithelial and fibrous elements. The ill-defined distinction betw een the two components in some cases earlier led to the assumption tha t these might be derived from the same (mesenchymal) stem cell. In thi s study, we investigated the distribution of extracellular matrix comp onents in 21 adamantinomas by immunohistochemistry, to gain informatio n on the interaction between the epithelial and fibrous parts of the t umor. Collagens I and III, and fibronectin were generally present in t he (osteo-)fibrous tissue of adamantinoma but lacked in the epithelial aggregates. There was a clear relation between the identification of the epithelial and fibrous components at the histological level, and t he staining for basement membrane proteins collagen TV and laminin. Pr ominent areas with cohesive epithelial growth were surrounded by conti nuous basement membranes, whereas less distinct epithelial islands con tained membrane interruptions or had no surrounding basement membrane at all. Tenascin stained intensely surrounding demarcated epithelial a ggregates, but weakly or absent more distantly. Osteofibrous dysplasia (OFD)-like tumors displayed local spicular density or pericellular st aining of basement membrane factors in fields of isolated keratin-posi tive cells. These findings suggest that in adamantinoma individual epi thelial cells transform from the osteofibrous tissue and thereafter fo rm clusters of epithelium, as can be recognized in classic adamantinom a. This is in analogy to the development of the glandular component of biphasic synovial sarcoma. The fibrous part of adamantinoma is, howev er, believed to be of benign nature. These results further substantiat e the hypothesis of osteofibrous dysplasia being a potential precursor lesion of adamantinoma. Copyright (C) 1997 by W.B. Saunders Company.