RESUMO
OBJECTIVES: The aim of this study was to correlate the imaging features with surgical histology for tibial osteofibrous dysplasia (OFD), osteofibrous dysplasia-like adamantinoma (OFD/LA) and classical adamantinoma and to determine the additional role of imaging in suggesting a correct diagnosis in cases of needle biopsy misdiagnosis. MATERIALS AND METHODS: This is a retrospective audit of 24 patients presenting over a 9-year period to a specialist orthopaedic oncology unit. Radiographic and axial magnetic resonance imaging (MRI) characteristics were recorded for each patient. The needle biopsy diagnosis and resection specimen histological diagnoses were retrospectively reviewed and compared with the imaging findings. RESULTS: The 24 cases comprised five OFD, 11 OFD/LA and eight adamantinoma based on surgical resection histology. The mean length of OFD was 6.1 cm (range 2-8.5 cm), for OFD/LA was 6.5 cm (range 2-13 cm) and for adamantinoma was 13.2 cm (range 6.5-26 cm). Seven of eight adamantinomas had moth-eaten margins compared to five of 11 OFD/LA and two of five OFDs. Three of eight adamantinomas demonstrated cortical destruction, with seven of eight cases completely involving the marrow cavity. In comparison, only one of 11 OFD/LA cases and one of five OFD cases demonstrated cortical destruction, and complete marrow involvement was rare. Four of 19 cases had a different needle biopsy result compared to the final histology, three cases being upgraded from an OFD/LA or OFD to classical adamantinoma. The radiological features of these three cases were more in keeping with a diagnosis of adamantinoma. CONCLUSIONS: A diagnosis of classical adamantinoma is suggested by an extensive lesion with moth-eaten margins and complete involvement of the medullary cavity on axial MR imaging. Misdiagnosis on needle biopsy may occur in up to one fifth of cases, and radiological features can assist in making the correct diagnosis.