Adamantinoma

Adamantinomas of long bones are a rare primary malignant bone tumour. They are not to be confused with an adamantinoma of the jaw. 

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 (1.3:1). Patients usually present with dull pain of gradual onset.

Pathology

Location

Occurrence almost exclusively confined to the tibial diaphysis (especially anterior cortex) ^2,5. Since it is a low-grade malignancy, it has the propensity to metastasise to distant locations including: lung, bone, lymph nodes, pericardium and liver. 

Radiographic features

Plain film and CT

Typically, it appears as a multi-locular or slightly expansile osteolytic cortical lesion. This may be visualised 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 tumour foci may be seen, defined as foci of high signal intensity on either T2- or T1-weighted contrast-enhanced images, interspersed with normal-appearing cortical or spongious bone ². Fluid-fluid level may occasionally be seen.

• C+ (Gd): tends to show intense and homogeneous static enhancement, although there is no uniform dynamic enhancement pattern ²

Treatment and prognosis

Surgical resection with en-bloc resection is often performed. It is a locally aggressive tumour 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 actual name "adamantinoma" was given by B Fisher in 1913 ⁹. 

Differential diagnosis

Imaging differential considerations include ⁶:

• chondromyxoid fibroma
• fibrous dysplasia
• osteofibrous dysplasia: has a more ground glass texture on CT