Adamantinoma of long bones is a rare low-grade malignant bone tumor most often arising in the tibia, but also occasionally exhibiting synchronous involvement of the ipsilateral fibula. Some adamantinomas have "osteofibrous dysplasia-like" features. 1 Thus, a relationship between adamantinoma and osteofibrous dysplasia (a benign fibro-osseous lesion occurring almost exclusively in the tibia of children less than 10 years of age) has been proposed. This relationship, however, is poorly understood.Cytogenetic analyses of adamantinoma and osteofibrous dysplasia are few. [2][3][4][5][6][7] In this study, the cytogenetic and molecular cytogenetic findings of four cases of adamantinoma and a review of the literature are presented. Materials and Methods Case 1A 37-year-old female presented with a nontender protuberance in the midshaft of the right tibia known since childhood. As a child, she sustained a fracture of the tibia with minimal trauma. The fracture was treated in a cast and healed without complications. For 20 years, the protuberance remained unchanged in size and character and without symptoms. In 1999, however, she sustained a fracture of the tibia once again and with minimal trauma. Plain radiographs demonstrated a pathological fracture through a destructive process including the lesion and protuberance. A biopsy revealed adamantinoma. A radical en bloc resection of the right tibial diaphysis and reconstruction using fresh frozen allograft tibia, plates, and autologous bone graft were performed.Histopathologically, both the biopsy and resected specimens were composed of epithelial-like cells arranged in large islands or nests embedded in a densely fibrous stroma. Mitotic figures could not be identified. Immunohistochemical staining revealed that the epithelial cells were immunoreactive for cytokeratin (AE1:AE3). The histopathological diagnosis was classic adamantinoma. Case 2A 20-year-old male sought medical attention because of pain in the anterior aspect of his right leg with recreational running. Four years earlier, the patient had noted a bulge on the anterior border of his right tibia. Plain radiographs revealed a bubbly lesion involving the anterolateral cortex of the midshaft of the right tibia. Comparison with previous radiographs over the past 4 years showed indolent progression (Figure 1). Magnetic resonance imaging (MRI) demonstrated a multilobulated mass that uniformly enhanced with contrast. A bone scan showed intense uptake confined to the site of the lesion seen in the plain radiographs and revealed no other areas of significant skeletal uptake. An incisional biopsy was followed by a wide local excision and reconstruction.Microscopically, the lesional tissue was intracortical. At the periphery, the cortex demonstrated enlarged Harversian canals filled with a paucicellular fibroblastic reactive tissue. There was a transition from mature to less mature bone tissue, or so-called zoning. The center of the lesion