Adamantinoma is known as a low-grade malignant biphasic tumor. Classic adamantinoma is in general characterized by admixture of both epithelial and osteofibrous components that are associated with various proportions and differentiation patterns. Osteofibrous dysplasia (OFD) is a self-limited benign fibro-osseous lesion of bone during infancy and childhood. OFD-like adamantinoma is characterized by predominance of osteofibrous tissues, in which small groups of epithelial cells are only detected by careful search or immunohistochemistry. There have been controversies as to the potential correlation among OFD, OFD-like adamantinoma and classic adamantinoma. We report an unusual case of adamantinoma arising in the tibia, with an extensive review of the literature. The present findings suggest a direct correlation between OFD-like adamantinoma and classic adamantinoma. At the age of 12 years, the tibial biopsy lesion was diagnosed as OFD. At the age of 23, the lesion became larger and more destructive on x-ray films. The biopsy lesion was diagnosed as classic adamantinoma. Wide excision was performed. The primary lesion was retrospectively diagnosed as OFD-like adamantinoma because of presence of keratin-positive epithelial cells within the stroma. At five years after surgery, the patient was free from recurrence or metastasis. The retrospective histological findings of OFD-like adamantinoma in the original biopsy and of a classic adamantinoma in all sections of the later resection specimen raised the possibility of an unusual progression of OFD-like adamantinoma to a classic adamantinoma. The present case and the literature review suggest that an OFD-like adamantinoma may be a precursor lesion of classic adamantinoma. Therefore, the possibility of progression of OFD-like adamantinoma to a classic adamantinoma should be kept in mind, particularly when the destructive changes are seen radiologically.
2006 Tohoku University Medical Press