Value Of DWI Combined With Conventional MRI In The Differential Diagnosis Between Ovarian Fibrothecomas And Malignant Pelvic Solid Tumors

PartⅠCorrelation between MRI Features of Ovarian Fibrothecomas and PathologyObjective:To improve the diagnostic accuracy of ovarian fibrothecomas preoperatively by discussing and comparing their MRI and pathological features.Methods:35 fibrothecomas in 33 patients confirmed by surgery and pathology were retrospectively analyzed in Xinhua hospital from May 2009 to March 2015.The clinical materials,MRI characteristics and pathological features were reviewed and ADC values of the solid component were measured.The χ² test was used to compare the difference of degenerative changes between tumors smaller and larger than 6 cm.P<0.05 was considered statistically significant.Results:Age:mean,58.5±12.7 years.Component:solid,n=30;cystic,n=5.Size:mean,70.3±41.8mm.T1WI:isointensity,n=35.T2WI:hypointensity,n=17;isointensity,n=9;hyperintensity,n=2;mixed intensity,n=6.DWI:grade 1,n=19;grade 2,n=10;grade3,n=6.Enhancement degree:minor,n=20;mild,n=13;marked,n=2.Pelvic fluid:none,n=4;minor amount,n=16;small amount,n=9;large amount:n=4.Degenerative changes:present,n=22;absent,n=13.Endometrial hyperplasia:present,n=3;absent,n=30.The lowest ADC value:mean,1.16±0.27×10^-3 mm²/s.The mean ADC value:mean,1.25±0.28×10^-3 mm²/s.Degenerative changes between tumors smaller and larger than 6 cm was significantly different（P<0.001）.Pathologically,tumors with more fibroblasts tended to show hypoinitensity and tumors with more theca-like cells tended to show hyperintensity on T2WI and DWI.Conclusions:Fibrothecomas mostly affect menopausal and postmenopausal women.They usually manifest as round or oval solid masses with clear borders and smooth margins.Degenerative changes occur more often in tumors with diameters more than 6cm.Most thecomas/fibrothecomas show isointensity on T1WI and hypo/isointensity on T2WI with minor to mild enhancement.On DWI,they mostly show low or slightly high intensity.Nevertheless,high or very high intensity can occur.Tumors with more fibroblasts tended to show hypoinitensity and tumors with more theca-like cells tended to show hyperintensity on T2WI and DWI.Part Ⅱ Value of DWI Combined with Conventional MRI in the Differential Diagnosis between Ovarian Fibrothecomas and Malignant Pelvic Solid TumorsObjective: To assess the value of diffusion weighted imaging（DWI）combined with conventional MRI in the differential diagnosis between fibrothecomas and malignant pelvic solid tumors.Methods: 35 fibrothecomas in 33 patients and 40 malignant pelvic solid tumors confirmed by surgery and pathology were retrospectively analyzed in Xinhua hospital from May 2009 to March 2015.The clinical materials and MRI features were reviewed and ADC values of the solid component were measured.The statistical comparisons for the clinical and image features between groups were conducted by using the univariate analysis.The receiver operating characteristic（ROC）curve was also used to compare the ability of the lowest ADC value and the mean ADC value in differentiating thecomas/fibrothecomas from malignant pelvic solid masses.The cut-off value was obtained by calculating the maximum Youden index.The multivariate logistic analysis was performed to show the true prognostic value of ADC value and the other MRI characteristics.P < 0.05 was considered statistically significant.Results: All the thecomas/fibrothecomas showed isointensity on T1 weighted imaging（T1WI）and 74.3% lesions showed hypo-to isointensity on T2 weighted imaging（T2WI）.After administration of contrast medium,94.3% tumors appeared as minor to mild enhancement.On DWI,they showed a diversity of low to very high signal intensity.All malignant pelvic masses manifested as hyperintensity on T2 WI and 87.5% tumors showed very high signal（grade 3）on DWI.The lowest ADC value and mean ADC value of thecomas/fibrothecomas were significantly higher than malignant pelvic solid tumors.In the ROC curve analysis,higher AUC and specificity could be achieved by using the lowest ADC value than the mean ADC value.When the lowest ADC value of 1.02 ×10^-3mm²/s was used as the cut-off value,sensitivity,specificity and the highest accuracy were 71.4%,87.5% and 80.0%,respectively.The multivariate logistic regression analysis showed that shape,signal intensity on T2 WI,capsule and the lowest ADC value were the significant indicators in discriminating thecomas/fibrothecomas from malignant pelvic solid tumors.Conclusions: The combination of DWI and conventional MRI is of great value in the differential diagnosis between fibrothecomas and malignant pelvic solid tumors.