After the concerned parties were aware of the usefulness of MRI examination in diagnosing uterine myoma, several reports have been published that discuss “differential diagnosis of uterine myoma and sarcoma” using MR images, with consideration of progress and development for this examination in the future. Initially, several reports regarding the differentiation between uterine myoma and uterine sarcoma by combining a variety of clinical findings with findings of tumor configurations shown in MR images were observed. However, gradually, researchers became aware of the limitations of this approach alone [
10,
11,
12,
13]. Recently, there have been several reports of differentiation methods using DWI and ADC. In other words, these are methods that compare the respective biofunctions between uterine myoma and sarcoma.
In 2008, Tamai et al. reported that with DWI, uterine sarcoma and cellular leiomyoma presented high signals, while ordinary leiomyoma and degenerated leiomyoma were depicted in low signals. They further investigated the comparison of ADC values, reporting that this enabled the differentiation of LMS and degenerated leiomyoma. Tamai et al. also reported that there were cases of overlapping ADC values for the three items of ordinary leiomyoma, cellular leiomyoma, and LMS [
14]. Subsequently, in 2009, Namimoto et al. combined tumor ADC values and the ratio of signal intensities in T2WI of the tumoral and normal myometrium, and they were able to reduce the overlap described above and reported moreover that this established the diagnosis of sarcoma with both for 100% sensitivity and specificity [
15]. In 2013, Thomassin-Naggara et al. reported the diagnosis of sarcoma with 92.4% accuracy through a combination of T2WI signal intensity (SI), DWI with a b-value = 1000 s/mm
2, ADC value (<1.23 × 10
−3 mm
2/s), and patient age [
16]. Furthermore, in 2014, Sato et al. reported five cases of LMS with ADC values less than 1.1 × 10
−3 mm
2/s in 10 areas within the sarcoma. They then combined DWI SI with ADC value (<1.1 × 10
−3 mm
2/s) and differentiated myoma from LMS with high accuracy [
17]. In 2015, Lin et al. found that while contrast-enhanced MRI resulted in a higher accuracy rate of diagnosis for sarcoma than DWI (
b-value = 1000 s/mm
2), the combination of DWI and ADC values (<1.08 × 10
−3 mm
2/s) established the diagnosis of sarcoma with accuracy rates equivalent to those of contrast-enhanced MRI. They reported that in patients with decreased renal function for whom contrast-enhanced MRI was difficult, discrimination with DWI was useful [
18]. Recently, there have been several reports arguing the usefulness of DWI and ADC values [
3,
19,
20,
21,
22]. However, in 2018, Kaganov performed a systematic review of past reports and found that a combination of T1WI and T2WI was effective, reporting that when there are high signals in T1 and high signals in T2, sarcoma can be diagnosed with 77.78% specificity. Kaganov found no significant association between ADC signals and sarcoma diagnosis [
22]. Nagai et al. created the PREoperative sarcoma score (PRESS) using the four factors, such as age at operation, serum lactate dehydrogenase level, MRI findings (high signals in T1WI and/or heterogeneous signals in T2WI), and endometrial cytology findings and reported the usefulness of the PRESS. However, the point that neither DWI findings nor contrast-enhanced MRI findings are used should be noted in this analysis [
23,
24]. There is no doubt that signal intensities in T1 and T2WI, DWI, and contrast-enhanced MRI findings are each useful in the diagnosis of sarcoma. Nevertheless, as shown in
Table 1, there is an overlap in MRI findings for myoma and sarcoma, which are not sarcoma-specific findings. Thus, currently, it is not the differentiation of sarcoma with high accuracy but surely “not to overlook even one single mass that may be a tumor” that is important.