Epimetaphyseal lesions may occur within congenital dysplasia or can be linked to metabolic, inflammatory and systemic diseases. They can also be caused by trauma or be due to malign or benign neoplasms. Our case-report concerns a 4-year old boy who was x-rayed the day after falling from a chair and twisting his right ankle. X-ray showed an epimetaphyseal lesion of about 2 cm in diameter, located eccentrically in the lateral site of the distal tibia. A unilamellar periostal reaction could be detected in the lateral slices. On MRI, the lesion seemed to be of chondromatous origin and showed smooth borders with no evidence of surrounding oedema. The adjacent epiphyseal plate appeared as untypically fragmented. In CT-scans, the ventrolateral cortical bone was partially perforated and the lesion showed a tender sclerotic border. Due to the benign aspect, we agreed upon radiologic controls in order not to harm the epiphyseal plate by biopsy. MRI follow-ups revealed a slight but continuous growth. The lesion assumed an increasingly eccentric, tongue-shaped configuration with simultaneously increasing calcifications and mineralisations. After 5 years of radiological surveillance, the patient showed no evidence of growth-disturbance and did not report pain, but an increasing feeling of pressure when wearing boots. Traumatic causes as well as metabolic, inflammatory and systemic diseases can, considering the patient’s history and clinical status, be put aside. The benign aspect combined with the long-term follow-up rules out malignancies. A chondroid matrix with increasing areas of mineralisation imply the diagnosis of a chondromatous tumour, although radiomorphology does not support this assumption; especially not, if age, clinical presentation, eccentric epimetaphyseal location and the involvement of the epiphyseal plate are taken into account. Among the entities left for differential-diagnosis, a dysplastic process e.g. Dysplasia hemimelica, must be considered, although doubts remain. For confirmation of diagnosis, further radiological and clinical surveillance will be conducted.
