Recently, MRI was considered better than CT for the detection and staging of gynecological and pelvic malignancies [10].
This study included 50 endometrial focal lesions that were grouped according to histopathology into a benign group (28 lesions) and a malignant group (22 lesions). Endometrial hyperplasia was the most common benign lesion (n = 15) followed by endometrial polyps (n = 6), while endometrial carcinoma was the most common malignant lesion (n = 17) followed by choriocarcinoma (n = 5).
Our results are in agreement with those of Elsammak et al., who classified 42 lesions as benign (24 cases) and malignant (18 cases) groups according to their histopathology results and found that the most common benign lesion was endometrial hyperplasia, while the most common malignant lesion was endometrial carcinoma [3]. Additionally, Kilickesmez et al. reported that endometrial carcinoma was the most common malignant endometrial lesions [11]. Kececi et al. found that 40/42 of the studied malignant lesions were endometrial carcinoma, while 7/14 of the studied benign lesions were endometrial polyps: 5 were submucosal fibroids and only 2 lesions were endometrial hyperplasia [12].
In the current study, conventional MRI showed relatively low diagnostic accuracy in the differentiation of different endometrial focal lesions, as most of the studied benign and malignant lesions showed an iso-low signal intensity on T1-WI and an intermediate-high signal intensity on T2-WI with the exception of five submucosal fibroids that showed low signals on both T1-WI and T2-WI and two focal adenomyosis that showed increased thickness of the junctional zone with low signal foci on T1- and T2-WI but with bright dots on T2-WI.
Our results were in a concordance with those of Kierans et al., who reported that conventional MRI features regarding morphology and signal characteristics were not significantly different in both benign and malignant endometrial pathologies [13]. Additionally, other studies have shown that endometrial polyps and benign hyperplasia often present as a focal mass occupying the uterine cavity or as nonspecific endometrial thickening, and those signs are not sufficient for accurate diagnosis of carcinoma, hyperplasia, and polyps [10]. Tamai et al. reported that ordinary leiomyomas exhibited low signals on both T1- and T2-weighted images [14].
DW-MRI is a functional imaging technique that does not require the exogenous contrast medium administration required [15]. When DWI is combined with MRI, it becomes a good diagnostic tool and provides more information for the differentiation and extension of benign and malignant lesions [16].
According to the present work results, DWI could aid in the differentiation between benign and malignant focal endometrial lesions as most of the studied benign lesions (23/28) showed negative diffusion results, and the remaining 5 submucosal fibroids showed T2-WI blackout effects. The ADC values of benign lesions were found to be relatively high when measured at high b value (b = 1000m2), ranging from 1.36 to 1.89 × 10−3 mm2/s (M = 1.52 ± 0.25 × 10−3 mm2/s), although they were very low for the submucosal fibroids ranging from 0.79 to 0.86 × 10−3 mm2/s (M = 8 ± 0.27). On the other hand, 21/22 malignant endometrial focal lesions were diffusion positive (restricted diffusion), with only 1 endometrial carcinoma that was diffusion negative. The ADC values of the malignant endometrial focal lesions were relatively low ranging from 0.636 to 1.241 × 10−3 mm2/s (M = 0.95 ± 0.24 × 10−3 mm2/s) when measured at high b value (b = 1000).
These results are consistent with the results of Elsammak et al. [3], who found a significant difference between the mean ADC values of malignant masses (0.82 ×103 mm2/s) and benign lesions (1.44 × 10−3 mm2/s), and those of Kececi et al. [12], who revealed that the mean ADC value of 42 malignant lesions (0.94 ± 0.18 × 10−3 mm2/s) was statistically significantly lower than the mean ADC value of benign lesions (1.45 ± 0.22 × 10−3 mm2/s) (P < 0.01), and matched also with Fujii et al. [17], who concluded that malignant tumors namely endometrial carcinoma and carcinosarcoma show lower ADC values than benign tumors. Also, Thulaseedharan et al. [18] and Heo et al.’s [19] studies showed that there was a much lower ADC value for malignant endometrial lesions compared to the benign endometrial lesions.
Our findings as regards DWI results of Submucosal fibroids with the findings of Thomassin-Naggara et al. [20], that revealed DWI low signal intensity for all leiomyomas and as well Namimoto et al. [21] who stated that all studied ordinary leiomyomas (n = 95) were diffusion negative with low SI on DWI, however, Shen et al. [22] stated that submucosal myomas had different mean ADC values that may overlap with malignant lesions.
In our study, conventional MRI study only correctly diagnosed 39/50 studied lesions, achieving 77.27% sensitivity, 78.56% specificity, 78% accuracy, 73.91% PPV, and 81.48% NPV. When adding DWI with ADC value measurements at high b value (b = 1000), we could correctly diagnose 47/50 lesions that increased diagnostic sensitivity to 95.45%, specificity to 92.86%, and accuracy to 94%, as well as PPV to 91.3% and NPV to 96%.
Our results were in harmony with Elsammak et al.’s [3] results which concealed that conventional MRI could correctly diagnose 36/42 cases, achieving 77.8% sensitivity, 99.17% specificity, 87.5 PPV, and 84.6% NPV, and matched also with Bharwani et al. [23] who stated that the addition of DWI to conventional MRI has increased the sensitivity and specificity to 86% and 100%, respectively, in the diagnosis of uterine endometrial lesions; Takeuchi et al. [24, 26] reported a sensitivity and specificity of DWI in endometrial lesions which were 100% and 81%, respectively.