summary Adamantinomas are rare, low-grade malignant tumors of unknown etiology that are almost always located in the diaphysis of the mid-tibia. The condition usually presents in patients who are between 20 and 40 years old with regional pain and a palpable mass. Diagnosis is made with a biopsy showing nests of epithelial-like cells arranged in palisading or glandular pattern, in a background of fibrous stroma. Treatment is usually wide-margin surgical resection. Epidemiology Incidence less than 300 cases have been documented Demographics occurs in young adults (20 - 40 years of age) Anatomic location almost always located in mid-tibia Etiology Pathophysiology unknown Associated conditions osteofibrous dysplasia historically, it was thought that osteofibrous dysplasia (OFD) was a precursor to this adamantinoma, however current studies have cast doubt on this theory Presentation Symptoms pain of months to years duration Physical exam bowing deformity or a palpable mass of tibia is common Imaging Radiographs multiple sharply circumscribed lucent lesions ("soap bubble" appearance) with interspersed sclerotic bone in mid-tibia some lesions may destroy cortex may see bowing of the tibia radiographic evolution of lesions is helpful in the diagnosis as lesions may continue to grow and erode thru the cortex unlike other primary bone tumors, adamantinoma typically shows no periosteal reaction Studies Histology biphasic contains both epithelial and fibrous mesenchymal cells nests of epithelial-like cells arranged in palisading or glandular pattern stain for keratin background of fibrous stroma Differential Osteofibrous dysplasia differentiating between osteofibrous dysplasia and adamantinoma is critical osteofibrous dysplasia is benign and treated with observation adamantinoma is malignant and treat with surgical resection Differential diagnosis of Adamantinoma Tibial diaphysis lesion Treated with wide-resection alone Adamantinoma o o Osteofibrous dysplasia o Chondrosarcoma o Parosteal osteosarcoma o Treatment Operative wide-margin surgical resection indications standard of care in most patients techniques often requires intercallary resection with allograft or intercallary megaprosthesis reconstruction as adamantinoma is a low-grade malignancy, radiotherapy and/or chemotherapy is not typically used for local control of disease Prognosis May metastasize to lungs (25%), therefore long-term followup is recommended Recurrence is uncommon with negative margin excision