Admantinoma is a rare primary tumour of long bones was so named because of its resemblance to ameloblastoma (adamantinoma) of the mandible. It was first described by Fischer in 1913
Tibia is most common site of admantinoma. The lesion has a strong predilection for the tibia in about 90 percent of cases. It has been found in other long bones, such as the ulna, humerus, femur,fibula, and capitate.
It is a diaphyseal tumor.
Multifocal involvement of the tibia and fibula has been reported; in one patients in addition to the tibia and fibula the femur was also affected.
Adamantinoma is a tumor of adult life with a median age occurrence of the mid-thirties. It occurs with equal frequency in males and female. However, occurrence in adolescence and, rarely, in childhood has been reported.
Types of Admantinoma
Adamantinomas are classified into two 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. The two types of adamantinomas have distinct radiographic and histologic differences.
The presenting complaint is local pain with an insidious onset, developing over a period of several months to years. There may be a history of trauma. On palpation there is localized hard swelling and tenderness of a varying degree.
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.
The lesion is commonly located in the middle third of the diaphysis of a long bone; it may, however, extend to either end to involve the metaphyses. On rare occasions, with aggressive adamantinomas, the epiphysis may be affected. Primary location in the epiphysis has not been reported.
The radiographic appearance depends on the site of origin of the tumor-whether intracortical or intramedullary.
The internal radiographic pattern may be one of several types:
- A solitary area of irregular rarefaction in the cortex, which is expanded on its outer surface
- Bubbled locules in which multiple areas of expanded cortical rarefaction are separated by delicate step
- Sawtoothed lysis caused by external subperiosteal bone erosion
- Fibrosclerosis, which consists of numerous small areas of cortical rarefaction with sclerotic margins.
There is little if any periosteal reaction. In intracortical lesions there may be marginal buttressing.
In the intramedullary types of admantinoma the radiographic pattern may be circumscribed lytic, multilocular expansile, or satellite sclerotic; on rare occasions intramedullary lesions may resemble reticulated honeycomb or be frankly destructive.
Scintigraphy with technetium-99m will show increased uptake in the lesional area. The periphery of the area of increased uptake on the scan corresponds to the rim of the reactive zone about the lesion.
Computed tomography will clearly delineate the area of bone destruction-cortical or intramedullary, the nature of the reactive areas in the transition zone, and whether there is soft tissue extension.
CT and MRI are not specific in the differentiation of this tumor from other conditions and findings often overlap with those of other tumors and tumor-like lesions
Arteriography shows marked increased vascularity with abnormal vascular channels in the area of bone destruction.
Multiple areas of radiolucency with an admixture of sclerosis of the diaphyseal and metaphyseal regions of a long bone may be seen in a number of other bone tumors.
Benign lesions to consider in the differential diagnosis are
- Fibrous dysplasia
- Nonossifying fibroma
- Desmoplastic fibroma
- Osteofibrous dysplasia
- Periosteal fibroma
- Aneurismal bone cyst
- Brown tumor
- Haemophilic pseudotumor
- Hydatid bone cyst
- Lytic phase of Paget’s disease
Malignant lesions to consider in the differential diagnosis
- Fibrosarcoma, reticulum-cell sarcoma, osteogenic sarcoma, and metastatic carcinoma.
Treatment of Admantinoma
Marginal excision often results in recurrence.
It is recommended that the tumor be excised by a wide surgical margin.
In the tibia, if the tumor has penetrated the medullary canal, a full segmental resection is performed in order to achieve a wide surgical margin; an allograft is utilized for reconstruction.
If the tumor is well marginated and intracortical, involving the anterior cortex only, an attempt may be made to preserve the posterior cortex to facilitate reconstruction; it should, however, be understood that it carries a greater risk of recurrence.
When adamantinoma is aggressive, extending into soft tissues, or when attempted segmental resection has failed and there is aggressive recurrence, a below-knee amputation or knee disarticulation is performed.
If pulmonary metastases develop they are removed by wide excision.
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