10-year-old male patient presented with an 18 month history of pain and swelling of the left tibia.
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.
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.
Adamantinoma
Based on the provided X-ray and MRI images of the left tibia, there is a notable osteolytic destruction and expansile lesion in the tibial shaft. The lesion boundaries are poorly defined, and “moth-eaten” edges can be observed. In some regions, the cortex appears thinned or even destroyed. On MRI T1-weighted and T2-weighted sequences, the lesion spans a large area, with heterogeneous signal changes within the medullary canal, suggesting it has involved or invaded the bone marrow cavity. Surrounding soft tissues also show a certain degree of involvement and swelling. A bone scan indicates increased radiotracer uptake in the left tibial shaft, suggesting active local bone metabolism.
Considering the patient’s age (10 years), the duration of localized pain and swelling (18 months), and the imaging findings (involvement of the medullary canal with expansile bone destruction), Adamantinoma is a strong possibility despite the pediatric age group. The lesion appears to involve the full thickness of the marrow cavity, which supports this consideration.
However, there is some radiological overlap between Adamantinoma and Osteofibrous Dysplasia, and the patient is relatively young. Therefore, a prompt biopsy and histopathological examination are recommended for definitive diagnosis. If confirmed as Adamantinoma, a more aggressive treatment strategy should be considered.
Rehabilitation should be carried out under the guidance of orthopedic and rehabilitation specialists, with a gradual, individualized plan. For pediatric patients with such tibial lesions, the following principles (FITT-VP) can be referenced:
This report is based on the provided history and imaging findings and serves only as a reference for analysis. It does not replace in-person consultation or professional medical advice. In the event of any doubts, please consult a specialist for personalized diagnosis and treatment planning.
Adamantinoma
