4. Borderline epithelial ovarian tumours (BEOTs), also
known as tumours of low malignant potential, account
for 4–14 % of all epithelial ovarian tumours (EOTs).
Although uncommon, peritoneal implants or metastatic
lymphadenopathy may occur in patients with BEOTs.
Clinically, BEOTs are distinct from ovarian malignant
epithelial tumours (MEOTs) in that they often affect
young women of childbearing age.
Patients with BEOTs are more likely to have early stage
disease, and generally have an excellent prognosis after
surgical excision but a high recurrence rate.
5. It is important to preoperatively discriminate BEOTs from
MEOTs because a conservative fertility-sparing
laparoscopic surgery can be performed in the former.
Magnetic resonance (MR) imaging is gaining recognition as
a complementary method to ultrasound in the diagnosis of
complex adnexal masses because of its excellent capacity
for tissue characterization.
The addition of DW imaging to conventional MR imaging
seems to improve accuracy in differentiating benign from
malignant ovarian lesions.
6. Concerning ovarian lesions; Thomassin-Naggara reported
that simultaneously low signal intensity within the solid
component on T2-weighted and on b 1000 DWI suggested
benignity of complex adnexal mass.
To authors’ knowledge, the utility of DW imaging in the
differentiation of BEOTs and MEOTs has not been
reported.
The purpose of this study was to investigate whether DW
imaging is a useful tool in distinguishing BEOTs from
MEOTs.
8. Study population
This retrospective study was approved by authors’
institutional review boards and informed consent was
obtained from all patients.
Patients with suspected ovarian tumours on the basis of
elevated CA 125 level, ultrasound or CT were enrolled in
an ovarian tumour MR imaging study project from
October 2009 to September 2012.
Among 365 cases proven by surgery and pathology, a
total of 102 patients were found with non-benign EOT
including 60 BEOTs in 48 patients and 65 MEOTs in 54
patients.
9. Study population
Patients’ ages ranged from 17 to 71 years (mean, 39.5±15.3
years) in the borderline group and 40–75 years (mean, 55.3±9.4
years) in the malignant group.
The radical surgery, consisting of TAH+BSO, omentectomy,
multiple peritoneal biopsies, retroperitoneal lymph node
sampling, and cytological analyses of ascitic or peritoneal lavage
fluid, was performed in 70 patients (16 patients with BOETs and
54 patients with MEOTs).
The non-conservative surgery of BSO with or without
hysterectomy was performed in 19 patients with BEOTs.
The conservative surgery of unilateral salpingo-oophorectomy
was performed in 13 patients with BEOTs.
11. MR imaging technique
MR imaging was performed using a 1.5-T unit (Avanto or
Symphony, Siemens, Erlangen, Germany) with a phased
array coil.
Spasmolytic drugs were not administrated.
Patients in the supine position breathed freely during
acquisition.
The imaging range was from the inferior pubic symphysis
to the renal hilum and was extended beyond the dome of
tumour in the cases with huge masses.
12. MR imaging technique
Routine pelvic MR images were acquired as follows:
Axial T1-weighted imaging (T1WI).
Axial T1WI with fat suppression
Axial and sagittal T2-weighted imaging (T2WI) with or without fat
suppression.
Axial DW imaging was then obtained using echo planer imaging
sequence with diffusion gradient b factors, 0 and 1,000 s/mm2;
and acquisition time, 2 min 46 s.
Axial dynamic gadolinium-enhanced fat-suppressed T1WI was
performed immediately after intravenous injection of 0.1
mmol/kg of contrast material at a flow of 2.5 ml/s;
13. MR image analysis
MR images were read by two radiologists in consensus with
10 and 29 years of experience in gynaecological imaging.
Both of the radiologists were blinded to the clinical data of
patients.
The morphological features (tumour size, presence of solid
component) were determined on T2WI and contrast-
enhanced T1WI.
The term “solid component” included the solid portions,
papillary projections and thickened septa (larger than 5
mm).
14. MR image analysis
The signal intensity (SI) of tumour on DW imaging was
classified as high (similar to the SI of nerve root), moderate
(similar to small intestine) or low (lower than small
intestine).
On the ADC maps, a circular region of interest (ROI) of at
least 1 cm2 was placed at targeted areas with the possibly
lowest ADC values in the cystic and/or solid components of
tumour, by referring to conventional MR images, including
contrast-enhanced images and carefully avoiding areas
such as haemorrhage, necrosis, major vascular structures,
and artefacts such as chemical shift and magnetic
susceptibility artefacts.
15. MR image analysis
To eliminate the potential influence of intraindividual
correlation in patients with bilateral tumours (n=23), only
the results for the most complex tumour were considered;
thus, 102 tumours (48 BEOTs, 54MEOTs) were evaluated.
Also the analysis of ADC values of solid components
smaller than 10 mm (10 BEOTs and 3 MEOTs) were
excluded because of low contrast-to-noise ratio and
motion artefacts.
At least three measurements were obtained and averaged.
19. DW imaging findings
The mean ADC value and DW imaging SI of the cystic
component did not differ significantly between the two
groups.
20. Axial T2- weighted with fat suppression (a) and T1-weighted contrast enhanced images (b)
demonstrate a cystic mass with multiple septa and a papillary projection extending from
the cyst wall. The projection (arrow) shows high signal intensity on DW imaging (c) and has
an ADC value of 0.607×10−3 mm2/s (d)
A 42-year-old woman with ovarian mixed adenocarcinoma.
21. Axial T2-weighted with fat suppression (a) and T1-weighted contrast enhanced images (b)
demonstrate a solid mass (arrow). The mass shows high signal intensity on DW imaging (c)
and has an ADC value of 0.891×10−3 mm2/s.
A 40-year-old woman with ovarian serous adenocarcinoma.
22. Axial T2-weighted with fat suppression (a) and T1-weighted contrast-enhanced images (b)
show a unilocular cystic lesion with a large papillary projection demonstrating obvious
contrast enhancement (arrow). The papillary projection shows moderate signal intensity on
DW imaging (c) and has an ADC value of 1.486×10−3 mm2/s (d).
A 20-year-old woman with ovarian serous borderline tumour.
23. Axial T2-weighted with fat suppression (a) and T1-weighted contrast enhanced images (b)
demonstrate a right-sided solid mass (arrows) and a left-sided cystic mass with intracystic
papillary projections. The solid component shows low to moderate signal intensity on DW
imaging (c) and an ADC value of 1.975×10−3 mm2/s and 1.869×10−3 mm2/s in the right and
left masses, respectively.
A 27-year-old woman with bilateral ovarian serous borderline tumours.
25. MR imaging has shown a high diagnostic specificity for
some types of ovarian masses, such as dermoid cysts,
endometrial cysts and fibromas. However, there is no
specific role for conventional MR imaging in
characterizing borderline and malignant EOTs.
The presence of a contrast-enhanced solid component
may be useful for distinguishing malignant from benign
epithelial tumours but not for borderline from malignant
tumours.
26. In this study, most (54/60) BEOTs demonstrated at least
one of the imaging features which were recognized to be
associated with malignancy, such as irregularly thickened
wall, enhancing vegetation and predominantly solid mass.
Some studies show that DW imaging can differentiate
malignant from benign ovarian tumours with higher DWI SI
and lower ADC values in malignant tumours. However, no
significant ADC value difference was found between the
two groups.
The inconsistent results are probably due to the diversity
of samples and histopathological complexity of the ovarian
tumours.
27. Also some benign solid tumours such as teratomas or
fibrothecomas have lower ADC values that compromise the
higher ADC values in benign and borderline epithelial
tumours.
So, in this study, these non-epithelial tumours were ruled
out because of their characteristic findings on conventional
MR imaging.
28. In this study, most BEOTs demonstrated low or moderate
SI in the solid component on DW imaging, whereas almost
all MEOTs demonstrated high SI in the solid component.
The mean ADC value of the solid component in BEOTs was
much higher than in MEOTs.
Furthermore, the study showed an optimal ADC value
threshold of 1.039×10−3 mm2/s for differentiating
borderline from malignant tumours with a sensitivity of
97.0%, a specificity of 92.2% and an accuracy of 96.4 %.
29. When the solid component was too small to measure
the ADC value, a high DW imaging SI often suggested a
MEOT.
Therefore, both the assessments of DW imaging SI and
ADC value were useful in differentiating BEOTs from
MEOTs.
30. Although the radical surgery is the usual treatment for
BEOTs, the need for this procedure is controversial, as no
significant differences in the recurrence and mortality
between patients with radical and conservative surgeries
have been observed.
The conservative surgery has been recommended in
young patients with an early stage BEOT, even with a
stage II, III or IV BEOT, if they wish to maintain their
fertility.
The accurate characterization of BEOTs in the present
study will encourage the implementation of conservative
fertility-sparing surgery, especially the minimally invasive
laparoscopic surgery.
32. First, DW imaging was acquired through free-breathing
imaging which may affect the ADC value of lesions,
especially huge cystic lesions.
Second, the precise matching of histological specimens
taken for cell density measurement to the ADC value
measurement of the tumour may be difficult in the
mucinous BEOTs.
Third, the ADC value of solid component was not assessed
in 10 of 48 BEOTs and 3 of 54 MEOTs, as the solid
component was smaller than 1 cm.
Fourth, the ADC value threshold is machine-specific and
probably not universal.
33. Conclusion
The utility of DW imaging can discriminate BEOTs
from MEOTs, thereby improving the accuracy of
pretreatment and surgical management of EOTs.