Malignant round cell tumours of bone: atypical clinical and imaging features.

OBJECTIVE

To describe the clinical, radiological and MRI features of six atypical cases of histologically proven appendicular Ewing sarcoma/primitive neuroectodermal tumour (PNET).

DESIGN

Retrospective review of case notes and available imaging was carried out.

PATIENTS

Six patients (4 male, 2 female; mean age 27 years, range 19-44 years), presenting over a 77-month period, were identified from the Bone Tumour Register. All had unusual clinical and imaging features for Ewing sarcoma/PNET.

RESULTS AND CONCLUSIONS

Four tumours were centred on the distal femoral metaphysis, one in the proximal tibial metaphysis and one in the distal tibial metaphysis. Plain radiographs were available in four cases and showed minor cortical changes. MRI demonstrated a relatively small, eccentrically located intraosseous component with a large, eccentric extraosseous component. Extension into the epiphysis was seen in three cases and into the adjacent joint in two cases. Intraosseous "skip" metastases were present in three cases. The clinical and imaging features were atypical for conventional intraosseous Ewing sarcoma/PNET and the exact site of origin (intraosseous, periosteal or soft-tissue) was unclear.