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A rare, primary low-grade malignant bone tumor that occurs in more than 80% of cases on the anterior surface of the tibia (tibial dyaphysis). Most cases are symptomatic or present with pain, swelling, bowing deformity or pathological fracture. Metastases especially in the lungs may be observed.
ORPHA:55881Classification level: Disorder
AD represent between 0.1 and 0.5% of all primary malignant bone tumors. The life time prevalence in Europe is estimated to be 1/900,000. Males are more commonly affected and in the latter case the tumor is more aggressive.
AD affects individuals over a wide age range (2-86 years), but 75% occurs in the mature skeleton within the second and third decades. AD has an insidious onset and the typical presentation is that of a slow growing and painless swelling on the anterior side of the tibia. Localized pain, pathological fracture and bone deformity are other features which lead the patient to seek medical attention. Most tumors are located in the middle third of the tibial anterior cortex but involvement of bones other than the tibia has been reported and includes the humerus (6 %), ulna (4 %), fibula (3 %), femur (3 %) and radius (1 %). In rare cases, the tumor can be located in the ribs, pelvis, spine, carpus and tarsus. Multiple locations or purely within the cortex may be observed.
The etiology of AD is unknown and to date, no known genetic mutations have been identified. A translocation t(7;13)(q32;q14) has been reported in a lung metastasis from an AD of the tibia in a boy. However, an identical translocation was found in his normal father.
On conventional radiography, early stage AD appears as a cortical lucency without a significant periosteal. Cortical thickening, although seen after fracture and presence of a soft tissue mass are rare findings. Detection of tumors at this stage is rare and usually fortuitous, with most patients being diagnosed in more advanced stages. The typical tumors are multiloculated cystic/sclerotic lesions with a characteristic `soap bubble like' appearance. In some cases, the cortex may eventually be disrupted and a soft-tissue component can be found. Lesions are mostly eccentric, expansile and cortically located. AD show low signal intensity on T-1 weighted MRI and high signal intensity on T-2 weighted images. In histopathological terms, AD is characterized by the presence of a variable proportion of epithelial cells within osteofibrous tissue that may be intermingled with each other in various proportions resulting in 2 differentiating patterns: osteofibrous dysplasia-like AD (with a predominance of the osteofibrous component) with intermediate malignancy potential; and classic AD with a predominance of the epithelial component and low grade malignancy.
The main differential diagnosis for AD is fibrous dysplasia of bone but chondrosarcoma, langerhans cell histiocytosis, haemangioendothelioma (see these terms), fibroma (non-ossifying as well as ossifying), and bone cyst should also be excluded.
Management and treatment
Definitive cure can only be achieved after gross total resection with wide resection margins. Chemotherapy and radiotherapy do not play a role in the treatment of ADs. Long-term clinical and radiological monitoring is necessary because of the risk of local recurrence or metastasis, which can occur many years after the initial treatment.
In general ADs have a good outcome. Complete remission can be achieved in around 70% of the cases. However, in 10-50% of cases, the disease may be fatal due to metastases (occuring most often in the lungs and in the lymph nodes, although metastases to liver, bone and brain have been reported). Mean survival of patients with metastatic disease is reported to be 12 years.
A summary on this disease is available in Español (2014) Français (2014) Nederlands (2014) Deutsch (2007) Italiano (2007)