A 33-yr old man presented with a slowly progressive swelling in the middle 113d of his right tibia. X-rays examination revealed multiple sharply demarcated radiolucent lesions separated by areas of dense and sclerotic bone. Microscopic examination of a biopsy specimen revealed island of epithelial cells in a fibrous stroma. Which of the following is the most probable diagnosis?

Adamantinoma of long bone Introduction: Unusual neoplasm, almost always located in tibial shaft. Clinical features: Localized swelling and pain for several years. Age: Between 15-55 yrs. Radiological features: * An eccentric well demarcated area of destruction usually involving the anterior poion of the tibial shaft. * Slight expansion and coical thinning, with a cystic or multiloculated appearance is usual. * Periosteal Reaction is not marked. * Coical destruction on may be extensive. * Margins of tumors vary from being sharply and clearly demarcated, with slight sclerotic areas, to a hazy zone of transition of several mm, comparable to that seen in giant cell tumors. Histologically difficult to distinguish from metastatic adenocarcinoma, but component of the tumor may suggest an epithelial derivation. Although the tumor continues to grow to a slow rate, it is featured by local recurrent and eventual lung metastasis.