Objective: We correlated MR imaging findings with those from flow cytometry and determined prognostic factors of patients with major salivary gland lesions.
Subjects and methods: DNA ploidy (11 aneuploid, 35 diploid lesions) and S-phase fraction (SPF) (12 high-SPF, 28 low-SPF lesions) percentages as determined by flow cytometric technique in 46 major salivary gland lesions were correlated with MR findings and signal-intensity ratios of lesion to muscle on fast spin-echo T2-weighted images, unenhanced spin-echo T1-weighted images, and gadolinium-enhanced fat-suppressed spin-echo T1-weighted images. SPF percentages were correlated with the three signal-intensity ratios by stepwise regression analysis. Prognostic indicators of disease-free survival were assessed with Cox multivariate analysis (range of follow-up, 2-50 months; mean, 16.6 months).
Results: Signal-intensity ratios for all pulse sequences were significantly smaller in aneuploid lesions than in diploid lesions. Incidence of ill-defined margins (p < .001), invasion (p = .014), and hypointensity to the gland on T2-weighted images (p = .047) was significantly higher in aneuploid lesions than in diploid lesions. Of these, signal-intensity ratios on enhanced T1-weighted images were most accurate for predicting aneuploidy. A threshold of 1.55 for signal-intensity ratios on enhanced T1-weighted images yielded the highest accuracy (86%) for aneuploidy. Signal-intensity ratios on T2-weighted images (p = .025) and enhanced T1-weighted images (p < .001) were significantly smaller in high-SPF lesions than in low-SPF lesions. A threshold of 1.73 for signal-intensity ratios on enhanced T1-weighted images yielded 73% accuracy for high-SPF lesions, which was inferior to the prediction possible from ill-defined margins (80% accuracy). Aneuploidy (p = .008), ill-defined margins (p = .036), and signal-intensity ratios on unenhanced T1-weighted images (p = .008), related significantly and negatively to disease-free survival. A signal-intensity ratio of 1.22 or less for unenhanced T1-weighted images indicated a high risk of developing recurrence (100% sensitivity).
Conclusion: MR findings and signal-intensity ratios can reflect DNA ploidy and SPF status and can predict prognoses for patients with major salivary gland lesions.