Fig. 1.

A 33-year-old male with a history of nonspecific back pain and associated paraspinal mass, now presenting with lower back and lower left extremity pain with stiffness. Initial contrast-enhanced CT scan in the axial (A–C) and coronal (D–E) views with three-dimensional volume rendering (F) demonstrated the known retroperitoneal mass measuring 8.2 × 6.5 × 13.7 cm (arrows–B, D, F). involvement of the left psoas muscle was observed with no clear plane of separation (arrow – A). Sclerotic changes with cortical disruption were visualized along the left anterolateral aspects of L4 and L5 (arrow–C, E).