Introduction
Background
Adamantinoma is a rare tumor, and its origin remains controversial. Fischer first described the tumor in 1913,7 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.
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.1,2
Pathophysiology
Although adamantinomas can cause a variety of pathologic and histologic abnormalities, the tumors are usually lobular and well defined. Generally, adamantinomas remain intracortical; however, when prior surgery has been performed or when the tumor is of the classic type, the lesions may extend beyond the periosteum.
The histologic features of adamantinomas have a multitude of variations that are present not only among patients but also among different areas of the same tumor. The histologic features of differentiated adamantinomas are predominantly characterized by a pattern of osteofibrous dysplasia. Conversely, in classic adamantinomas, the cells form a tubular, basaloid, squamoid, or spindled pattern. As a result of the variety of manifestations of the tumor, multiple biopsies must often be performed to obtain a representative sample for study.
Adamantinomas typically range from 3-15 cm in size, and metastases occur in approximately 15-20% of patients. Metastases generally appear in the lungs and local lymph nodes. Adamantinomas can be found in many other bones in addition to their usual location in the tibia. The humerus, ulna, femur, fibula, and radius are other possible locations in the long bones. Occasionally, the tumor occurs in the spine. Adamantinomas are locally aggressive and extremely slow growing.
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Frequency
United States
Because only approximately 200 well-documented cases of adamantinoma have been identified in the almost 100 years since the tumor has been classified, it can be described only as extremely rare.
International
Adamantinomas are extremely rare.
Mortality/Morbidity
Despite their slow-growing nature, adamantinomas can cause significant morbidity and mortality. The 10-year survival rate is estimated to be approximately 10%. In addition, painful bowing deformity of the tibia is not an infrequent occurrence in this condition.
Race
To the authors' knowledge, no racial comparative studies have been performed because of the infrequent occurrence of the tumor and because of the difficult and technologically sophisticated diagnosis. Knowing how many cases have been missed in the less developed regions of the world is impossible, just as knowing how many cases remain undiagnosed in industrialized Western nations is difficult.
Sex
Adamantinomas have a male predominance, with an approximate male-to-female ratio of 1.25:1.
Age
The more common classic adamantinoma usually occurs in individuals older than 20 years, whereas the differentiated form of the tumor almost exclusively occurs in those younger than 20 years. However, the tumors have occurred in individuals aged 10-70 years.3
Anatomy
The tibia is by far the most commonly affected bone; tibial tumors account for 80-85% of primary adamantinomas. Other long bones are also commonly affected; occasionally, primary involvement of the spine occurs.
Presentation
Patients present with complaints such as a dull ache or bone pain that has been present for months to years. Another common complaint is localized swelling. Often, a history of trauma may be elicited. A palpable mass may be firm or soft; its diameter is usually in the range of 3-15 cm.4
Preferred Examination
Plain radiography, CT, and 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.5,6
Limitations of Techniques
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.
Differential Diagnoses
Aneurysmal Bone Cyst
Chondromyxoid Fibroma
Chondrosarcoma
Fibrous Dysplasia
Other Problems to Be Considered
Eosinophilic granuloma
Hemangioendothelioma
Nonossifying or ossifying fibroma
Osteofibrous dysplasia
Simple bone cyst
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References
Dorfman HD, Czerniak. Bone Tumors. Mosby-Year Book;1998:949-73.
Kitsoulis P, Charchanti A, Paraskevas G, Marini A, Karatzias G. Adamantinoma. Acta Orthop Belg. Aug 2007;73(4):425-31. [Medline].
Gleason BC, Liegl-Atzwanger B, Kozakewich HP, Connolly S, Gebhardt MC, Fletcher JA, et al. Osteofibrous Dysplasia and Adamantinoma in Children and Adolescents: A Clinicopathologic Reappraisal. Am J Surg Pathol. Mar 2008;32(3):363-376. [Medline].
Jain D, Jain VK, Vasishta RK, Ranjan P, Kumar Y. Adamantinoma: A clinicopathological review and update. Diagn Pathol. Feb 15 2008;3(1):8. [Medline].
Resnick D. Diagnosis of Bone and Joint Disorders. Vol 6. Philadelphia, PA: W. B. Saunders Co;1995:3882-4.
Taveras JM. Radiology, Diagnosis, Imaging Intervention. Vol 5. Philadelphia, PA: Lippincott Williams & Wilkins;1993.
Fischer B. Uber ein primares Adamantinom der Tibia. 12. Frankfurt: Zeitschr. f. Path.; 1913:422-441.
Further Reading
Keywords
long bone tumors, classic adamantinomas, differentiated adamantinomas, adamantinomous tumors, primary adamantinomas
