Major salivary gland lesions: correlation of MR findings with flow cytometric DNA analysis and prognosis.

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.