Adamantinoma

Myrtha Cesar, MD candidate
Kitt Shaffer, MD, PhD

May 11, 1998

Presentation

Imaging Findings

Anteroposterior radiographs of the left tibia demonstrate an 11 cm intramedullary expansile lytic lesion at the distal end of the diaphysis (white arrows) with sclerotic changes superiorly (black arrows). Thinning of the medial osteal surface is apparent, but there is no evidence of periosteal reaction. A STIR image demonstrates increased signal in the region corresponding to the lytic lesion on plain films (white arrow) and decreased signal in the periphery of the lesion (black arrow), consistent with sclerotic changes. A coronal T1-weighted magnetic resonance (post gadolinium) image demonstrates peripheral enhancement of the lesion (arrow) and a 1 cm extension of the tumor into the local soft tissue. Hemorrhage is unlikely as no fluid is apparent.

Differential Diagnosis

• giant cell tumor
• fibrous dysplasia
• adamantinoma
• bone cyst
• aneurysmal bone cyst
• eosinophilic granuloma
• osteomyelitis

Diagnosis

Discussion

Radiographically, adamantinomas are sharply circumscribed lesions with lucent filling defects (central or eccentric in location). The tumors are separated from normal bone cortex by a sclerotic zone. Periosteal reaction is generally absent unless the lesion is accompanied by pathologic fracture.

Gross pathology shows a well-demarcated lesion with peripheral lobulated contours. Cystic cavities contain either straw-colored fluid or blood, and the lesion may contain spicules of bone. The tumors are usually eccentrically located in the bone, sparing the medullary cavity. Microscopically, adamantinomas consist of epithelial-like cells in tubular or spindle configuration. The cells stain (immunohistochemical) strongly for keratin.

The tumors are locally aggressive and metastesize to lung and local lymph nodes in 20% of cases. Treatment consists of wide-block excision of the involved segment of bone. The tumor readily recurs if not completely removed.

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