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.

Epidemiology

Typically presents in the 2^nd to 3^rd 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.

Pathology

Location

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.

Radiographic features

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.

MRI

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 cases¹.

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.