Morphological differences between schwannomas and ganglioneuromas in the mediastinum: Utility of the craniocaudal length to major axis ratio

Objective: To evaluate the diagnostic value of the craniocaudal length (CC) to major axis ratio (CC/M R) for differentiating between schwannoma and ganglioneuroma in the mediastinum on CT/MRI.

Methods: 22 schwannomas (Group A: 7 schwannomas in the posterior mediastinum; Group B, 15 schwannomas located in the chest wall or regions of the mediastinum other than the posterior mediastinum) and 14 ganglioneuromas in the posterior mediastinum (Group C) were evaluated. For each tumour, the major and minor axes on the largest transaxial image and the CC were measured on CT/MRI. The CC/M R was calculated, and differences among the three groups were analysed.

Results: The major axis, minor axis and CC measurements and CC/M R ranged from 23 to 52mm (mean, 37 mm), 15 to 38mm (28 mm), 25 to 62mm (42mm) and 0.66 to 1.4mm (1.1 mm), respectively, in Group A; from 18 to 97mm (37 mm), 10 to 71mm (28 mm), 18 to 80mm (35mm) and 0.59 to 1.3mm (0.95 mm), respectively, in Group B; and from 20 to 70mm (49 mm), 15 to 60mm (32 mm), 30 to 110mm (74mm) and 1.0 to 2.6mm (1.5 mm), respectively, in Group C. The mean CC/M R of Group C was significantly higher than those of the other two groups (p<0.005). There was no difference between the mean CC/M R of Groups A and B.

Conclusion: Ganglioneuromas display higher mean CC/M R than schwannomas. The CC/M R is a useful index for differentiating between these neurogenic tumours.

Advances in knowledge: The CC/M R is a practical and effective index for differentiating between ganglioneuromas and schwannomas.