Malignant Mesenchymoma Presenting as a Paraspinal Mass in a 14-year-old Boy

HS Fung, JLY Leung, SJ Shu, YL Lam, ACL Chan, SCH Chan

Hong Kong J Radiol 2004;7:149-53

Malignant mesenchymoma is a rare soft-tissue tumour. We report a case of malignant mesenchymoma in a 14-year-old boy who presented with a rapidly growing mass on his back. Computed tomography revealed a slightly hypodense tumour with heterogeneous contrast enhancement and focal calcification in the right paraspinal region. In T1- weighted magnetic resonance images, the tumour appeared slightly hyperintense relative to skeletal muscle; short T1 inversion time inversion-recovery images showed a heterogeneously hyperintense tumour with minimal perilesional oedema. Heterogeneous contrast enhancement was noted in magnetic resonance images after intravenous gadolinium administration. Pathological examination of the resected specimen showed a malignant mesenchymoma with components of leiomyosarcoma and osteosarcoma. This case illustrates that definitive diagnosis of malignant mesenchymoma can be reached only when the tumour is thoroughly sampled and examined.