Diagnostic Studies. The radiographic appearance consists of multiple small, oval, radiolucent cortical defects with a distinct margin of reactive bone and a thickened cortex. Adamantinoma typically has a “soap bubble” appearance with distinct multiloculated lesions that expand the cortex into the soft tissue. The differential diagnosis includes chondromyxoid fibroma (see Plate 6-7), ossifying fibroma, osteofibrous dysplasia (primarily in patients younger than 10 years old), monostotic fibrous dysplasia (see Plate 6-8), and infection.

Definitive information about extension along the medullary canal or into adjacent soft tissue is obtained by MRI.

Histologic examination reveals a classic pseudoglandular appearance with epithelioid cells with nuclear palisading (single file pattern) that may suggest rounded islands of glandular tissue consistent with adenocarcinoma.

Treatment/Prognosis. The treatment of choice is resection where possible, usually with a segmental resection of the tibia that can be reconstructed with autograft bone. More conservative treatment (curettage or marginal excision) is associated with repeated recurrences, which ultimately may require amputation, and occasionally patients develop pulmonary metastases. With adequate local control, the prognosis is good.