Keywords
Hydropic degeneration - leiomyoma - magnetic resonance imaging - split fiber sign
Introduction
Extensive hydropic degeneration in uterine leiomyoma is a rare occurrence and is commonly
reported in association with pregnancy. It mimics malignancy due to rapid growth and
atypical imaging appearances. Awareness of the imaging features helps in diagnosis,
avoids unnecessary patient anxiety, and hence reassurance especially when encountered
in pregnancy. We report two cases of extensive hydropic degeneration of leiomyoma
in nonpregnant females with imaging and histopathology correlation. We also propose
the “split fiber” sign as a useful magnetic resonance imaging feature for diagnosing
this condition.
Case Reports
Case 1
A 37-year-old female presented to the surgical outpatient department with complaints
of lower abdominal distension and vague pain for 2–3 months. No fever or altered bowel
habits were present. Her menstrual cycles were regular. Her last child birth was 8
years ago and was a normal vaginal delivery. No past history of abdominal surgery
was elicited. Per abdomen examination revealed a firm mass in central and lower quadrants.
She was then referred to radiology department for further evaluation. Transabdominal
ultrasonography (USG) was done followed by magnetic resonance imaging (MRI) pelvis.
USG revealed a large predominantly isoechoic (to myometrium) mass with peripheral
areas of patchy heteroechogeneity [Figure 1]. It was seen to arise from the posterior uterine wall compressing the uterus. On
color Doppler, moderate vascularity was seen in the mass that was closer to the uterine
attachment and sparse vessels seen peripherally. A linear defect in myometrium was
seen at the mass attachment in continuity with the endometrium. Both ovaries and the
endometrium were otherwise unremarkable.
Figure 1 (A-C): (A and C) Transabdominal ultrasonography in sagittal plane shows a large mass predominantly
isoechoiec to the myometrium with peripheral heteroechoic areas related posteriorly
to the uterus compressing the same with suspicious luminal communication (white arrow
in C). (B) On Doppler USG, the mass shows prominent vascularity especially near its
uterine attachment. (M -mass, U-uterus, B- urinary bladder)
MRI pelvis was done without contrast with routine T1 turbo spin echo (TSE), T2 TSE
with and without fat saturation along with diffusion weighted imaging (DWI) and fast
field echo (FFE) in orthogonal planes. The origin of the mass from the posterior uterine
wall was confirmed on MRI. The mass measured approximately 19 × 16 × 12 cm and extended
till supraumbilical level. The mass had roughly two parts. The part that was closer
to its origin was isointense to the myometrium with multiple vascular channels within
and the periphery showed fluid-like hyperintensity on T2 weighted sequence with sparse
vessels [Figure 2]A, [Figure 2]B, [Figure 2]C, [Figure 2]D. The peripheral T2 hyperintense zone was divided by multiple curvilinear isointense
strands [Figure 2]D. Continuity with the endometrial cavity at the mass attachment was seen at the
torus uterinus. No hemorrhagic areas were seen on FFE with DWI showing mild variable
restriction. The imaging features were in concern for malignancy and a provisional
diagnosis of primary sarcoma or sarcomatous change in a fibroid or aggressive angiomyxoma
was considered. Possible trans myoendometrial extension and fistulization with the
cavity was sought. Exploratory laparotomy with hysterectomy was done, which revealed
a large exophytic mass arising from the posterior uterine wall. Cut section revealed
a severely edematous tissue in periphery with firm tissue and prominent blood vessels
at the attachment site. Histopathology showed extensive fluid accumulation between
the smooth muscle proliferation along with cystic changes [Figure 3] along with few preserved areas of more compactly arranged whorls of smooth muscle
cells. No obvious myxomatous areas were seen.
Figure 2 (A-D): (A) On MRI T1 weighted axial section the mass (M) shows roughly two components, isointense
to the myometrium with vascular channels closer to the uterine origin (white arrow)
and hypointense peripherally. (B-D) MRI T2 weighted images in axial, sagittal and
coronal sections. The mass is seen to compress the uterus anteriorly with confirmation
of the origin (white dotted arrow in C). Linear hypointense areas are seen within
the peripheral hyperintensity corresponding to fibers split up by the edema / fluid
accumulation (arrow heads in D)
Figure 3: Microphotograph (Hematoxylin and Eosin stain - x40 magnification) showing sparse
cellularity and separation of the smooth muscle fibers by intercellular fluid/edema
(arrows). Asterix refers to normal non degenerated portion of fibroid
Case 2
A 47-year-old female with dysmenorrhea was referred to radiology department for an
USG examination of the pelvis. Her menstrual cycles were irregular and painful for
4–5 months period. No other relevant history was elicited. On transabdominal USG,
the uterus was mildly enlarged. A posterior intramural fibroid was seen. Endometrial
cavity revealed a heteroechoic mass with linear echogenic areas measuring 9 × 5 cm
[Figure 4]. The mass showed very minimal peripheral vascularity. Endometrial mass versus a
degenerated submucosal fibroid was considered as possibilities and a MRI pelvis with
contrast was ordered.
Figure 4 (A and B): (A) Transabdominal ultrasound of pelvis shows a relatively iso- hypoechoiec mass
within the endometrial cavity (white arrow).Note a subserosal fibroid in left posterolateral
wall (white dotted arrow). (B) No vascularity seen on color Doppler
On MRI, the mass was predominantly hyperintense on T2 weighted sequence and isointense
on T1 weighted sequence. On T2, curvilinear hypointense strands were noticed [Figure 5]. The mass was submucosal arising from the anterior wall with focal isointensity
at the attachment site. Minimal fluid was seen within the endometrial cavity. On gadolinium
contrast, minimal linear enhancement was seen. The posterior intramural fibroid showed
avid enhancement. Based on the imaging features, degeneration (myxomatous/hydropic)
within the submucosal fibroid was considered. Patient opted for total hysterectomy.
Preserved gross specimen shows fleshy submucosal mass corresponding to the degenerated
leiomyoma [Figure 6]. Histopathology revealed extensive hydropic degeneration of the submucosal leiomyoma
[Figure 7].
Figure 5 (A-D): (A and B) T2 weighted MRI in axial, sagittal sections shows a mass arising from the
anterior submucosal myometrium and filling the endometrial cavity (white arrow). Arrowhead
is the compressed endometrium. Dotted arrow is the posterior subserosal fibroid. (C)
T1 post gadolinium contrast in axial sections depicts no enhancement of the submucosal
mass (white arrow) as opposed to the fibroid posterolaterally which shows homogenous
enhancement (dotted arrow). (D) T2 weighted MRI in axial section shows linear hypointense
areas corresponding to split fibers (arrowheads)
Figure 6: Post operative specimen showing the degenerated submucosal fibroid (black arrows)
with whorls and clefts. White arrow is the endometrial cavity
Figure 7: Microphotograph (Hematoxylin and Eosin stain - x40 magnification) showing sparse
cellularity and separation of the smooth muscle fibers by intercellular fluid/edema
(arrows). White block arrow is a focal cystic change
Discussion
Uterine leiomyomas are very commonly seen in reproductive age females (25–30%) and
are benign proliferation of smooth muscle cells separated by fibrous tissue and are
hormone dependent.[1] They are commonly referred to as fibroids or just myomas. Up to 20–50% are symptomatic
with symptoms depending on the size, location, and complications.[2] Complications include degeneration, torsion, or rupture. Different types of degeneration
include hemorrhagic (red), cystic, calcified, myxomatous, lipomatous, and sarcomatous.
Rarer forms of degeneration include hydropic and cotyledonoid types, though the latter
refers to an atypical pattern of growth rather than degeneration.[3] The degenerations that occur in fibroid are rarely pure, as mixed types of degeneration
can be seen in a fibroid simultaneously on histopathology with imaging depicting the
predominant type.
Hydropic degeneration refers to extensive fluid accumulation within the fibroid. Hydropic
degeneration as a focal occurrence is seen in up to 50%.[4] Extensive hydropic degeneration is rare with few published case reports associated
with pregnancy [5],[6],[7],[8] and pose significant diagnostic dilemma due to rapid growth. Additionally, elevation
in CA-125 can be seen causing pseudo Meigs’ syndrome causing more challenge in diagnosis.[9],[10] Incidence of hydropic degeneration could not be found due to no large published
series in literature. Authors have proposed that venous outflow obstruction caused
by pregnancy could predispose to such extensive edematous changes within the leiomyoma
[5] apart from its hormone sensitiveness. Hydropic degeneration of leiomyoma in nongravid
female is much more rare.[11],[12]
As different forms of degenerations occur simultaneously in a given fibroid, the categorization
on imaging is based on predominant imaging feature. For example, a red degeneration
is suggested in the presence of hemorrhagic signals on T1, FFE sequences. Hydropic
basically means fluid, hence such degenerations follow fluid signal/density/echogenicity
on MRI/computed tomography (CT)/USG, respectively. Imaging can vary from entirely
cystic appearing to layers of fluid separating the fiber whorls.
On USG, hydropic degeneration can range from completely cystic, anechoic area to echogenic
foci, suggesting inter tissue fluid accumulation. On CT, hypodensity is expected,
but may not reliably differentiate. On contrast administration, degenerated areas
may not enhance.
MRI is the preferred modality for diagnosis of fibroid degeneration as it can depict
tissue characteristics such as hemorrhage/fluid/solid/necrosis with the use of multiple
sequences. A nondegenerated fibroid is isointense to myometrium on T1 and hypointense
on T2 sequences and shows avid enhancement post contrast. In hydropic degeneration,
the fibroid shows focal/diffuse T2 hyperintensity with reduced enhancement.[13] Extensive hydropic degeneration can mimic malignancy due to large size, rapid growth,
and T2 hyperintensities.[14] In such cases, careful observation of the splitting of the fibers by fluid can aid
in differentiating from malignant ones. Post contrast can also help in differentiating
as the hydropic degeneration does not enhance or show poor enhancement, whereas malignancies
usually show variable enhancement.
Sarcomatous changes within leiomyoma are rare, and differentiation of malignancy from
more benign changes, especially in pregnancy, is important for decisions on management.
Other imaging differentials for large uterine masses that show pregnancy-related growth
include malignant fibrous histiocytoma and aggressive angiomyxoma.
We propose a useful sign to differentiate hydropic leiomyoma from malignancy and we
refer to it as the “split fiber” sign. It refers to presence of curvilinear T2 hypointense
strands within the degenerated leiomyoma separated by the fluid accumulation and edema
[Figure 8]. This sign was seen in both the cases. A similar description of the sign was described
in the literature,[5],[8] but we first refer to it as the “split fiber” sign as an easy means to remember
and appreciate the imaging feature. Retrospectively, this sign was appreciated in
the T2-weighted images of reported cases in the literature.[5],[8] Similar appearance can be seen in myxomatous degeneration with myxoid stroma separating
the fibers, though commonly observed on histopathology.
Figure 8 (A-D): (A and B) Illustration of "split fiber" sign. Edema/intercellular fluid separating
the smooth muscle cells and fibrous tissue with corresponding histopathology (arrows
in C) and T2 weighted MRI image (arrowheads in D)
Conclusion
Though uterine leiomyoma is a common condition, degenerations are of rare occurrence.
Even rarer occurrence is the extensive hydropic type which closely resembles malignancy.
Diagnosis is important for management purpose and prognostication. We propose the
“split fiber” sign on MRI T2-weighted imaging, which can be used to differentiate
hydropic degeneration from other grave conditions. Our cases also describe the characteristic
MRI features in two proven cases not associated with pregnancy. A larger study evaluating
the utility of this sign is open for research.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms.
In the form the patient(s) has/have given his/her/their consent for his/her/their
images and other clinical information to be reported in the journal. The patients
understand that their names and initials will not be published and due efforts will
be made to conceal their identity, but anonymity cannot be guaranteed.
