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Adamantinomas are rare, slow-growing, primary malignant bone tumors that in the vast majority of cases occur in the tibia of young patients. They comprise <0.5% of all primary skeletal tumors11
In the past, ameloblastomas, which are benign, locally aggressive bone tumors of the mandible, were also known as adamantinomas of the mandible. The two entities are histologically unrelated, and for this reason, adamantinomas are no longer subcategorised as those of the mandible and those of long bones.
Typically presents in the 2nd to 3rd decades as a locally aggressive mass 3-15 cm in diameter. There is a slight male predilection (M:F = 1.3:1). Patients usually present with dull pain of gradual onset.
The occurrence is almost exclusively confined to the tibial diaphysis (especially the anterior cortex) 2,5. Since it is a low-grade malignancy, it has the propensity to metastasize to distant locations including lung, bone, lymph nodes, pericardium, and liver.
Plain radiograph / CT
Typically, it appears as a multilocular or slightly expansile osteolytic cortical lesion. This may be visualized as areas of lysis interspersed with areas of sclerosis 3. Lesions tend to have an eccentric epicenter 4 and a lack of periosteal reaction. There may be locally aggressive disease at presentation.
Some authors have distinguished two morphologic patterns 2:
solitary lobulated focus
multiple small nodules in one or more foci
In some patients separated tumor foci may be seen, defined as foci of high signal intensity on either T2 or contrast-enhanced T1-weighted images, interspersed with normal-appearing cortical or cancellous bone 2. A fluid-fluid level may occasionally be seen.
T1 C+ (Gd): tends to show intense and homogeneous static enhancement, although there is no uniform dynamic enhancement pattern 2
Treatment and prognosis
Surgical en bloc resection is often performed. It is a locally aggressive tumor with distant metastases reported in around 15% of cases 1.
History and etymology
Adamantinoma is derived from the Greek word "adamantinos", which means "very hard". It was first observed in the shaft of an ulna in 1900 by C Maier 8, who believed it was a carcinoma, although the term "adamantinoma" was coined by B Fisher in 1913 9.
Imaging differential considerations include 6: