Last revised by Liz Silverstone on 17 Mar 2024

Adamantinomas are rare indolent malignant bone tumors with a predilection for the tibial diaphysis. Following excision, local recurrence can be problematic and may occur after an interval of decades. Lymphadenopathy and metastases complicate <30% of cases 12.

Ameloblastomas, which are benign locally aggressive bone tumors of the mandible, were previously also known as adamantinomas of the mandible. Although the histology is similar, a common histogenesis is unproven.

Adamantinomas account for <1% of primary bone tumors and typically present between the 2nd and 5th decades. There is a slight male predilection (M:F = 5:4) 12.

Symptoms of pain, swelling and tibial bowing deformity are slowly progressive. Pathological fracture presents acutely.

A history of prior local trauma may be elicited in around 60%. Paraneoplastic severe hypercalcemia and pancreatitis have been reported 12.

Almost all cases occur in long bones and up to 85% occur in the mid tibial shaft. Some occur in the tibial metaphysis and up to 15% concurrently involve the fibula. Occasionally tumors arise in the fibula alone, the humerus, hand, foot, radius, femur, ribs, spine, facial bones or pretibial soft-tissues 12.

The histogenesis remains the subject of debate. The histology is heterogeneous and epithelial, synovial, endothelial and osseofibrous components have been demonstrated. Transformation of osseofibrous dysplasia or angioblastic derivation have been proposed. Extensive sampling of the most radiolucent areas is recommended for diagnosis 12.

Subtypes are distinguished by degree of differentiation, osseofibrous component, Ewing’s sarcoma-like components or areas of squamous cell carcinoma 12.

Tumors are positive for cytokeratins 5, 14 and 19, and the stromal component is positive for vimentin.

The tumor is typically well-circumscribed, expansile and multiloculated with a thin sclerotic rim and involves the anterior tibial diaphyseal cortex. It can spread into the medullary canal and soft-tissues. There may be multiple tumor nodules and concurrent involvement of the fibula.

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. Tumors may be locally aggressive at presentation.

MRI is essential to define disease extent pre-operatively. The disease may be unifocal or multinodular with skip lesions or periosteal involvement.

Tumor demonstrates high signal intensity on T2- or contrast-enhanced T1-weighted images, interspersed with normal-appearing cortical or cancellous bone 2. A fluid-fluid level may occasionally be seen.

Lesions are FDG avid.

Surgical en bloc resection with wide margins and subsequent reconstruction is preferred. Amputation is sometimes necessary particularly for local recurrence. Curettage should be avoided due to a high incidence of local recurrence.

Local recurrence has been described up to 36 years post resection and metastases occur in 15-30% of patients affecting lymph nodes, lungs, bone, liver, other abdominal viscera, retroperitoneum and pericardium.

10-year survival may be as high as 92% and recurrence-free survival approximately 72%. The optimal duration and frequency of follow-up has not been defined.

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:

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