Adamantinoma is a rare tumor, and its origin remains controversial. Fischer first described the tumor in 1913,
and since then, only approximately 200 cases have been reported. The tumor occurs almost exclusively in the long bones; tumors in the tibia account for more than 80% of cases. The diaphyseal region is the area most commonly affected.
(See the images below.)
Plain radiograph in a patient with adamantinoma reveals bony sclerosis, which is typical of a well-established adamantinoma. Courtesy of UCSD Medical Library.
CT scan in a patient with adamantinoma reveals an expansile lesion and superficial erosion on the surface. Courtesy of UCSD Medical Library.
Adamantinomas are classified into 2 distinct types: classic and differentiated. Classic adamantinomas usually occur in patients older than 20 years, whereas differentiated adamantinomas occur almost exclusively in patients younger than 20 years. In addition, the 2 classifications of adamantinomas have distinct radiographic and histologic differences.
Patients with adamantinomas present with variable signs and symptoms; most commonly, they report pain and swelling. The tumor is slow growing, and patients may describe discomfort lasting months to years. Although ascertaining accurate mortality statistics is difficult because of the extremely rare nature of this tumor, the 10-year survival rate is believed to be 10%. Treatment options for adamantinoma are surgical and include either marginal or en bloc resection. Unfortunately, neither radiation therapy nor chemotherapy has been proven effective in the treatment of this insidious tumor.
Plain radiography, computed tomography (CT) scanning, and magnetic resonance imaging (MRI) may all be used to help assess suspected adamantinomous tumors.
However, CT and MRI are not specific in the differentiation of this tumor from other conditions; findings often overlap with those of other tumors and tumor-like lesions. A variety of tumors and tumor-like lesions can mimic an adamantinoma. Histologic examination is key to the identification of an adamantinoma; the histologic features of these tumors have many variations.
Limitations of plain-film radiography include the relatively long list of differential diagnoses for adamantinoma. Many pathologic conditions that are as rare as or more common than adamantinoma demonstrate similar characteristics on plain radiographs, as well as CT scans and MRIs. This fact, coupled with the limited experience that most radiologists (and physicians in general) have in dealing with this tumor, makes the diagnosis and treatment of adamantinomas challenging.