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ORIGINAL ARTICLE
Year : 2019  |  Volume : 32  |  Issue : 1  |  Page : 106-111

The role of MRI in the differentiation between benign and malignant ovarian lesions


1 Radiodiagnosis Department, Faculty of Medicine, Menoufia University, Menoufia, Egypt
2 Radiodiagnosis at Ministry of Health, Port Foud Hospital at Port Said, Egypt

Date of Submission05-Aug-2017
Date of Acceptance08-Sep-2017
Date of Web Publication17-Apr-2019

Correspondence Address:
Sara S El-Kholy
Port Foud, Port Said, 42523
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/mmj.mmj_548_17

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  Abstract 


Objective
To determine whether conventional MRI and diffusion-weighted imaging (DWI) could help accurately in distinguishing benign from malignant adnexal masses.
Background
Characterization of ovarian lesions is of great importance in order to plan adequate therapeutic procedures. Ovarian neoplasms may be benign, borderline, or malignant. Using an imaging-guided approach based on their morphological appearance, we classified adnexal masses into three main groups: cystic, solid and complex cystic and solid. We also used DWI as an advanced magnetic resonance technique to achieve more accuracy of diagnosis.
Materials and methods
Thirty patients with initial undetermined ovarian lesions underwent pelvic MRI on 1.5-T magnet with a pelvic-phased array coil. The MRI protocol was done. All cases are operated; their pathological and laparoscopic results were compared with preoperative MRI results.
Results
In all, 62.5% of malignant cases are complex (cystic/solid); 95% of benign cases have no vegetations or papillary projections; 85.7% of heterogeneously enhanced lesions were malignant 62.6% of malignant cases show septations. Sensitivity, specificity, positive predictive value, negative predictive value and accuracy of conventional MRI have increased from 87.5, 86.4, 70, 95, 86.7%, respectively, for conventional MRI to 100, 93.3, 88.9, 100, 95%, respectively, for DWI.
Conclusion
MRI is an accurate modality for the differentiation of benign and malignant adnexal masses, especially with diffusion MRI which gives more accuracy.

Keywords: adnexal lesions, diagnosis, diffusion-weighted imaging, MRI


How to cite this article:
El-Wekil AM, Abdullah MS, El-Kholy SS. The role of MRI in the differentiation between benign and malignant ovarian lesions. Menoufia Med J 2019;32:106-11

How to cite this URL:
El-Wekil AM, Abdullah MS, El-Kholy SS. The role of MRI in the differentiation between benign and malignant ovarian lesions. Menoufia Med J [serial online] 2019 [cited 2019 May 21];32:106-11. Available from: http://www.mmj.eg.net/text.asp?2019/32/1/106/256124




  Introduction Top


Ovarian masses are a common finding in daily clinical practice and may be incidentally detected or identified in symptomatic patients. Characterization of an ovarian lesion represents a diagnostic challenge; it is of great importance in the preoperative setting in order to plan adequate therapeutic procedures [1].

In the evaluation of patients with adnexal lesions the MRI has become an important tool and solve the problem of adnexa; most malignant and benign lesions can be diagnosed by MRI with high confidence and high accuracy than other modalities [2].

MRI is well known to provide accurate information about hemorrhage, fat, and collagen. It is able to identify different types of tissue contained in pelvic masses, distinguishing benign from malignant ovarian tumors [3].

Recent developments in MRI techniques such diffusion-weighted imaging (DWI) increase the contrast between the lesion and the surrounding tissues and have magnified the role and potential of MRI in the female pelvis [4]. It provides image contrast that is dependent on the molecular motion of water, which may be altered markedly by the disease [5]. This molecular diffusion is known as Brownian motion; in the field gradients produce incoherent phase shifts that result in signal attenuation [4].

Apparent diffusion coefficient (ADC) is a quantitative derivative of DWI that can be expressed as a map or calculated as a value; multiple b values should be obtained to reduce the error in ADC calculation and improve tissue characterization [6]. When diffusion-weighted MRI is used in gynecologic applications, cancers have shown lower ADC values [7].

The aim of this study is evaluation of the MRI role in the discrimination between benign and malignant ovarian lesions in correlation with pathologic and laparoscopic results.


  Materials and Methods Top


Thirty patients with initial undetermined ovarian lesion were included in this study. The study was performed between February 2016 and January 2017 at a private center.

MRI

Pelvic MRI was performed on a 1.5 T magnet (PhilipsAcheiva, Guildford Business Park, Guildford, Surrey, UK) with a pelvic-phased array coil.

The MRI protocol was T1 in the axial plane, T2 in axial, coronal and sagittal, T1 postcontrast fat saturation in axial, coronal and sagittal and DWIs.

The inclusion criteria were: patients suspected to have a gynecological pelvic mass on clinical examination, having any gynecological troubles, history of previous ovarian tumor, age groups ranging from 20 to 73 years.

The exclusion criteria were: patients with past history of cardiac pacemaker or artificial valve, history of claustrophobia.

Ethical consideration: consent was taken from patients or their relatives before performing MRI and they had the right to refuse at any time. The study was approved by the Research Ethics Committee of the Faculty of Medicine, Menoufia University.

All patients were subjected to the following: full history taking and physical examination, routine laboratory investigation, ultrasound examination using transabdominal and transvaginal ultrasound approaches using 3–4 and 7–8 MHz probes, respectively, of an ultrasound machine (SonoscapeA5; Guangzhou Medsinglong Medical Equipment Co. Guangdong, China).

The MRI interpretations were the following.

MRI were analyzed for the following: MR appearance of the tumor; either cystic, solid or mixed; involvement of one or both ovaries; size of the lesion; signal intensity of the tumor; enhancement pattern, if present; wall thickness; presence of septations. MRI were analyzed for the presence of ascites, presence of infiltrated pelvic, or para-aortic lymph nodes.

Ovarian lesions can be classified according to the MRI morphological characters into three groups: cystic, solid and mixed cystic and solid.

Malignant MR criteria according to Valentini et al. [3] are: lesion size more than 4 cm, presence of solid components with heterogeneous enhancement, presence of papillary projections, thick septa more than 3 mm, presence of areas of necrosis and breaking down, enlarged, infiltrated lymph nodes more than 1 cm.

Interpretation of diffusion-weighted imaging

Qualitative analysis: regarding the signal intensity, we commented if the lesion shows low signal intensity on diffusion images with high signal in the corresponding ADC maps for benign masses or shows high signal intensity on diffusion images with lowering of the signal in the corresponding ADC maps for malignant masses. Quantitative analysis: regarding the quantitative analysis of DWI, we generated the ADC map, then we selected the region of interest manually on the solid and the cystic component of the tumors which was then automatically calculated on the workstation to obtain the ADC values. According to Zhang et al. [8] an ADC value of at least 1.20 × 10-3 mm 2/s may be the optimal cutoff for differentiating between benign and malignant tumors [Figure 1] and [Figure 2].
Figure 1: A 29-year-old-female patient with left tubo-ovarian abscess. MRI (a): sagittal T2, (b): axial postcontrast T1, shows left unilocular adnexal cystic mass measuring 10 × 5 cm; the lesion shows high signal in T2 with peripheral rim of low signal (blue arrowhead in a), the lesion has thick wall marginal enhancement (red arrowhead in b), lesion showed an ADC value of 0.74 × 10-3 mm2/s on ADC map. ADC, apparent diffusion coefficient.

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Figure 2: A 62-years-old-female patient with right malignant ovarian mucinous cystadenocarcinoma. MRI: (a) axial T2, (b) axial T1, and (c) diffusion-weighted image showing right multilocular adnexal complex cystic and solid mass measuring 13 × 10 cm. The lesion shows mixed intermediate and high signal in T2 (blue arrowhead in a) and mixed intermediate and low signal in T1 (blue arrowhead in b); the solid nodule shows high signal of restricted diffusion in DWI (red arrow in c); lesion showed an ADC value of 0.82 × 10-3 mm2/s on the ADC map. ADC, apparent diffusion coefficient; DWI, diffusion-weighted imaging.

Click here to view


All MRI results were compared with pathological and laparoscopic results; the later one classified the ovarian lesions into benign, borderline, and malignant lesions.

Statistical analysis

Data were fed to the computer and analyzed using SPSS (IBM Corporation, Armonk, New York, USA) release 15 for Microsoft Windows (2006). Qualitative data were described using number and percent. Quantitative data were described using range (minimum and maximum), mean, SD, and median. A P value of less than 0.05 was considered statistically significant. Comparison of numerical variables between the study groups was done using Student's t-test for independent samples. For comparing categorical data; χ2-test was performed. Accuracy was represented using the terms sensitivity, specificity, positive predictive value, negative predictive value, and overall accuracy.


  Results Top


The final study consisted of 30 female patients. The patient's age ranged from 20 to 73 years with a mean age of 40.37 years.

Results of histopathological and laparoscopic findings of benign and malignant lesions have shown that out of 30 patients, 22 (73.3%) were benign and borderline and eight (26.7%) patients had malignant masses, while the results according to MRI features were 20 (66.7%) cases were benign and borderline and 10 (33.3%) cases were malignant.

The most common site of the adnexal masses in both malignant and benign tumors was on the left site of the ovaries.

Of these, 59.1% of benign cases show high signal in T2-weighted images and only 37.5% of malignant lesions showed high signal in T2-weighted images; 9.1% of benign cases show fat density but no malignant cases show fat; 95% of benign cases have no vegetations or papillary projections and 62.6% of malignant cases show septations but only 36.4% of benign cases show septations.

85.7% of the heterogeneously enhanced lesions were malignant (six from total seven cases).

With DWI, 14 pathologically proved benign cases showed facilitated diffusion and eight benign cases showed restricted diffusion, only two malignant cases showed facilitated diffusion and six malignant cases showed restricted diffusion [Table 1].
Table 1: Characteristics of diffusion-weighted MRI findings with histopathological findings in the studied patients

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The mean ADC value of the solid component can differ significantly between benign and malignant masses (P < 0.001) as it was 1.176 × 10-3 ± 0.15 × 10-3 mm 2/s for benign tumors and 0.747 × 10-3 ± 0.12 × 10-3 mm 2/s for malignant tumors which was also considered statistically significant, while mean the ADC value of the cystic component did not differ significantly between benign and malignant masses (P = 0.195) as it was 1.603 × 10-3 ± 0.49 × 10-3 mm 2/s for benign tumors, and 1.223 × 10-3 ± 0.53 × 10-3 mm 2/s for malignant tumors which was considered statistically insignificant with an ADC value of at least 1.16 × 10-3 mm 2/s which may be the optimal cutoff for differentiating between benign and malignant tumors So the ADC value can be used as a considerable value in the differentiation between benign and malignant ovarian lesions only in solid components of lesions [Table 2].
Table 2: Validity of apparent diffusion coefficient in diagnosing malignant tumors

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The overall sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of conventional MRI were 87.5, 86.4, 70, 95, 86.7%, respectively.

Adding DWI (using ADC maps) to conventional MRI raises the overall sensitivity, specificity, PPV, NPV, and accuracy to 100, 93.3, 88.9, 100, 95%, respectively, according to the ADC values of the solid components which is considered statistically significant [Table 3].
Table 3: Apparent diffusion coefficient values of benign and malignant cases on cystic and solid components

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  Discussion Top


MRI provides exquisite views of the pelvic anatomy through its high spatial resolution and tissue contrast, and as such plays a key role in the work up of ovarian lesions, identifying features that distinguish benign and malignant lesions. In the case of primary tumors it enables local staging and detection of metastatic disease to help guide management options such as complex surgery or the consideration of neoadjuvant chemotherapy [9].

DWI is a new promising diagnostic tool that can be added to conventional MRI to better characterize and differentiate benign from malignant lesions [6].

In our study, we included 30 patients with different ovarian lesions and focused on the evaluation of the role of conventional MRI and diffusion MRI in differentiating between benign and malignant ovarian lesions.

In our study, the mean patient age was 40.37 years which disagreed with Koc et al. [10], study which carried on 58 female patients concluded that the mean patient age was 51 years; this disagreement may be attributed to the number of patients which is larger than ours.

In our study, 22.7% of total 22 benign cases showed a solid component and 62.5% of total eight malignant cases showed a solid component (P < 0.025), which was in agreement with Li et al. [11], study which concluded that solid components were found in 11/46 (23.9%) benign and 37/85 (43.5%) malignant masses (P < 0.05).

In our study, we found that 37.5% of malignant cases were cystic and 62.5% of malignant cases were mixed cystic and solid but no cases were solid only. This agrees with Amir et al. [2] study which found that malignant cystic lesions were 12.5 and 81.25% of malignant cases were mixed cystic and solid; he found only one case is pure solid (6%), we did not find any pure solid malignant lesion which may be attributed to our smaller number of malignant cases and also to the large size of malignant lesions under our study which made them more liable to necrosis and presence of cystic components.

In our study, we found that 59.1% of benign cases show high signal in T2-weighted images and only 37.5% of malignant lesions showed high signal in T2-weighted images. This disagree with Zhang et al. [8] study which found that 52.7% of studied benign lesions (39/74) show high signal in T2-weighted images and 84.3% of studied malignant lesions (108/128) show high signal in T2-weighted images; it may be attributed to our larger number of benign cases than malignant ones.

In our study, we found that 9.1% of benign cases show fat density but no malignant cases show fat density; 95% of benign cases have no vegetations nor papillary projections; 85.7% of heterogeneously enhanced lesions were malignant (six from total seven cases); 62.6% of malignant cases show septations but only 36.4% of benign cases show septations. This was in agreement with the study by Amir et al. [2] which was carried on 84 consecutive patients with different clinical presentations such as irregular menses, pelvic pain, fever, and palpable pelvic mass. He concluded that both benign and malignant masses of the ovary can be distinguished on MRI according to their texture whether cystic or solid, shape, size, invasion of adjacent tissue, contrast-enhanced T1-weighted MRI, fat-suppressed T1-weighted MRI, which may allow the diagnosis of benign adnexal masses with small amounts of fat and features of malignancy, such as enhancing mural nodules and/or enhancing solid areas with or without necrosis. The benign diagnosis can be on the basis of the fat component present, cystic composition and absence of septa or invasion of adjacent structures, while the malignant lesions contain solid components, nodules, vegetations [2].

In our study, we found that 80% of malignant lesions in the study (eight from total 10 malignant lesions) shows restricted diffusion with low ADC values. This agree with the Rajasri et al. [4] study which concluded that an adnexal mass with restricted diffusion usually is a malignant lesion.

In our study, we had 22 pathologically proven benign ovarian lesions; 14 cases showed facilitated diffusion and three cases of the rest eight cases are hemorrhagic cysts and chocolate cysts (endometriomas) which showed restricted diffusion due to high hemosiderin content; this was in agreement with the Nasr et al. [7] study which was conducted on 30 cases of different ovarian lesions; 23 cases were pathologically proved (classified to 12 benign and 11 malignant), seven cases showed facilitated diffusion (low signal in diffusion images, high signal on the corresponding ADC map and high ADC values), five hemorrhagic cysts (diagnosed by MRI criteria and follow-up ultrasonography) and two endometriomas (proved pathologically) showed high signal not only on diffusion images but also on the corresponding ADC map and ADC values [7].

In our study, the mean ADC value of the cystic component did not differ significantly between benign and malignant masses (P = 0.195) as it was 1.603 × 10-3 ± 0.49 × 10-3 mm 2/s for benign tumors, and 1.223 × 10-3 ± 0.53 × 10-3 mm 2/s for malignant tumors which was also considered statistically insignificant. This was in agreement with Li et al. [11] study which concluded that the mean ADC value of the cystic component is 2.58 × 10-3 ± 0.27 × 10-3 mm 2/s for benign tumors and 2.44 × 10-3 ± 0.33 × 10-3 mm 2/s for malignant tumors which were found to be statistically insignificant.

On the other hand, we found that the mean ADC value of the solid component can differ significantly between benign and malignant masses (P < 0.001) as it was 1.176 × 10-3 ± 0.15 × 10-3 mm 2/s for benign tumors, and 0.747 × 10-3 ± 0.12 × 10-3 mm 2/s for malignant tumors which were also considered statistically significant which was in agreement with the same study by Li et al. [11] which concluded that DWI is beneficial for differentiating between benign and malignant ovarian lesions regarding solid components as they found that the mean ADC value of the solid component is 1.69 × 10-3 ± 0.25 × 10-3 mm 2/s for benign tumors, and 1.03 × 10-3 ± 0.22 × 10-3 mm 2/s for malignant tumors which were found to be statistically significant.

In our study, we found that an ADC value of at least 1.16 × 10-3 mm 2/s may be the optimal cutoff for differentiating between benign and malignant tumors which was in agreement with the Zhang et al. [8] study carried out on 191 female patients with different ovarian lesions who underwent diffusion-weighted (DW) MRI of 202 ovarian masses aiming to evaluate the role of DWI in differentiating between benign and malignant ovarian lesions. They concluded that an ADC value of at least 1.20 × 10-3 mm 2/s may be the optimal cutoff for differentiating between benign and malignant tumors.

In our study, sensitivity, specificity, PPV, NPV, and accuracy of conventional MR imaging have increased from 87.5, 86.4, 70, 95, 86.7%, respectively, for conventional MRI to 100, 93.3, 88.9, 100, 95%, respectively, for DWI according to the ADC values of the solid components, which was in agreement with the Li et al. [11] study which concluded that the sensitivity, specificity, PPV, NPV, and accuracy of conventional MRI have increased from 91.8, 78.3, 88.6, 83.7, and 87.0%, respectively, to 96.5, 89.1, 94.3, 93.2, and 93.1% after adding DWI to the conventional MRI.


  Conclusion Top


MRI and clinical history may all help in narrowing the differential diagnosis of adnexal lesions. Certain MRI features and the pattern of enhancement on MRI are helpful in differentiating adnexal masses although the final diagnosis is based on histological examination. A combination of DWI with conventional MRI increases the accuracy of MRI to discriminate between benign and malignant lesions.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Figures

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    Tables

  [Table 1], [Table 2], [Table 3]



 

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