CASE 9383 Published on 22.06.2011

Rare case of tibial adamantinoma in 10-year-old immature skeleton

Section

Musculoskeletal system

Case Type

Clinical Cases

Authors

Bethapudi S, Ritchie DA, Straiton J

Patient

10 years, male

Categories
Area of Interest Musculoskeletal bone, Musculoskeletal system ; Imaging Technique MR, Nuclear medicine conventional
Clinical History
10-year-old male patient presented with an 18 month history of pain and swelling of the left tibia.
Imaging Findings
Plain radiograph of the left leg demonstrates grossly expansile lytic lesion involving the tibial diaphysis with invasion of the medullary cavity, ill defined zone of transition. No periosteal reaction, cortical destruction or soft tissue involvement is seen on the plain radiograph.

MRI examination confirms a low signal intensity T1 lesion with high signal on FLAIR and a homogeneous enhancement, post gadiolinium. There is complete invasion of the central medullary cavity. No skip lesions were identified.

Bone scintigraphy shows a solitary lesion at this site with increased radiotracer activity. The differential diagnosis at this stage included monostotic fibrous dysplasia, osteofibrous dysplasia and an adamantinoma (rare lesion in immature skeleton). An intralesional resection was performed with samples sent for histopathological analysis.

Histology of the specimen revealed osteo-fibrous matrix with solid nests of cytokeratin positive epithelial cells, findings in keeping with adamantinoma.
Discussion
Adamantinomas are relatively rare tumours accounting for approximately 0.1 to 0.4% of all primary bone tumours. These are considered to represent the aggressive end of the spectrum of fibro-osseous bone tumours, osteo-fibrous dysplasias representing the benign end. Unsurprisingly, given the wide variation in biological activities of these two conditions, the treatment options and overall management vary widely. Whilst adamanatinomas are treated radically with wide local excision, osteofibrous dysplasias can be closely monitored through regular follow up. Despite the cross-over of imaging findings of these related conditions, it is absolutely important that clinicians get the diagnosis right to avoid inappropriate surgical intervention, particularly in young patients.

Adamantinoma is a disease that commonly occurs in the 2nd and 3rd decades of life, although this has been reported in patients as young as 2 years of age. There is a particular prediliction for mid tibial diaphysis. Other long bones such as humerus, radius, ulna and femur can be rarely involved.

Biologically these are aggressive in nature and seen as expansile, lytic lesions on plain radiographs, with ill-defined moth eaten margins. They can be multifocal and can cause surrounding cortical destruction with involvement of the surrounding soft tissue swelling. Metastases to the lung have also been reported.

MRI is regarded as a very useful tool in evaluating the extent of the lesion and in aiding pre-surgical planning for assessment of potential resection margins. Complete invasion of the medullary cavity is the most important differentiating imaging feature of adamantinoma in comparison to osteofibrous dysplasia which commonly tends to confine itself to the cortex of the bone. Age of the patient is also an important differentiating factor, with osteofibrous dysplasias more commonly occurring in immature skeletons, particularly in children less than 10 years of age.

Adamantinomas commonly occur in fused mature skeletons. However, it is important to realise that this is not absolute as shown in the above case study. Besides, there can be considerable cross-over of imaging findings in atypical adamantinomas and osteofibrous dysplasias, for which the treatment and management options can vary widely. Whenever the imaging findings do not tie up with age and clinical presentation, threshold for performing a biopsy of the lesion for histopathological analysis should be low.
Differential Diagnosis List
Adamantinoma
Osteofibrous dysplasia
Fibrous dysplasia
Final Diagnosis
Adamantinoma
Case information
URL: https://www.eurorad.org/case/9383
DOI: 10.1594/EURORAD/CASE.9383
ISSN: 1563-4086