Can CT features differentiate between inferior vena cava leiomyosarcomas and primary retroperitoneal masses?

The objective of our study was to evaluate and describe CT features that may differentiate inferior vena cava (IVC) leiomyosarcomas from primary retroperitoneal masses.

A records search revealed 18 CT examinations with a soft-tissue mass contacting the IVC. Three readers evaluated the scans for four signs: an imperceptible IVC at the interface with the mass; a "positive embedded organ" sign (IVC embedded in the periphery of the mass); a "negative embedded organ" sign (IVC compressed at the perimeter of the mass); and tumor in the IVC lumen. CT findings were compared with pathology and operative reports. Performance and significance of CT features and interobserver agreement were calculated.

Four of 18 (22%) retroperitoneal masses were IVC leiomyosarcomas. The IVC was imperceptible at the interface with the mass in three of the four (75%) IVC leiomyosarcomas (κ = 0.88) and in no alternate diagnosis (p < 0.02). No IVC leiomyosarcoma showed a positive embedded organ sign versus one of 14 masses of alternate origin (p = 1.0, κ = 0.56). The negative embedded organ sign was seen in most primary retroperitoneal masses (11/14 or 79%, κ = 0.85) but in no case of IVC leiomyosarcoma (p = 0.01). Intraluminal tumor was seen in one of four (25%) IVC leiomyosarcomas and in two of 14 other retroperitoneal masses (p = 1.0, κ = 1.0).

An imperceptible IVC at the point of maximal contact with a retroperitoneal mass was the most useful CT feature for predicting the origin of IVC leiomyosarcoma. A negative embedded organ sign was useful for excluding IVC origin. Knowledge of these CT features may assist with preoperative planning.