AJR 2005; 185:216-218
© American Roentgen Ray Society
A Case of Struma Uteri
Mikio Akai1,
Hiroyoshi Isoda1,
Satoshi Sawada1,
Izumi Matsuo2,
Hideo Kanzaki2,
Noriko Sakaida3,
Akiharu Okamura3 and
Takako Kiyokawa4
1 Department of Radiology, Kansai Medical University, 10-15, Fumizono-cho,
Moriguchi, Osaka 570-8506, Japan.
2 Department of Gynecology, Kansai Medical University, Moriguchi, Osaka,
Japan.
3 Department of Surgical Pathology, Kansai Medical University, Moriguchi, Osaka,
Japan.
4 Department of Pathology, Jikei University, School of Medicine, Tokyo,
Japan.
Received January 12, 2004;
accepted after revision March 22, 2004.
Address correspondence to M. Akai
(mikio-akai{at}ninus.ocn.ne.jp).
Introduction
Teratomas of the uterus are very rare, with 17 cases reported
[1-3].
To our knowledge, a pure struma of the uterus has not been described in the
literature. We present the MRI features of a patient with this rare
entity.
Case Report
A 35-year-old woman was admitted to Kansai Medical University Hospital
because of a uterine mass with pelvic pain. She had had five pregnancies and
three full-term deliveries (one normal and two cesarean deliveries). At the
first cesarean delivery 8 years previously, a mass was found attached to the
uterus. On gynecologic examination, a large pelvic mass was found. A sonogram
showed a complex mass in the postuterine region. CA125, CA130, SLX (Sialyl
Lex-i antigen), and SCC (squamous cell carcinoma-related antigen) were within
normal ranges. A thyroid function test was not performed before the procedure.
After the procedure, the stock serum obtained preoperatively was measured, and
the result of thyroid function was normal. MRI revealed a complex mass with
small areas of T1 and T2 shortening and central areas of T1 and T2
prolongation in the postuterine region (Figs.
1A,
1B,
1C). The ovaries were separate
from the mass.
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Fig. 1B —35-year-old woman with pure struma of uterus. Sagittal
T2-weighted MR image (TR/TE, 4,000/124) shows lesion is represented as
hypointense mass with central hyperintense areas (arrows).
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Fig. 1C —35-year-old woman with pure struma of uterus. Sagittal
T1-weighted MR image (TR/TE, 550/12) shows mass as slightly heterogeneous and
more intense than muscle. T1-weighted image also shows central hypointense and
peripheral spotty hyperintense areas (arrows) in mass. On T2-weighted
image, peripheral spotty hyperintense areas on T1-weighted image are
hypointense to hyperintense (arrows in B).
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We thought the lesion was a mass with hemorrhagic necrosis because of small
areas of T1 and T2 shortening. Although the origin of the mass was not certain
based on the images, we considered it to be a leiomyoma because a
nondegenerated area within the lesion was hypointense, similar to the pelvic
muscles on T2-weighted images. Also, hemorrhagic necrotic areas were
occasionally seen in the leiomyoma, and subserosal leiomyoma often involved
the parauterine region. Various sarcomas, including leiomyosarcoma, are also
often seen as a mass with hemorrhagic necrosis in the postuterine region. In
the current case, we thought they were inconsistent with the slow growth of
the mass.
During surgery, an 11-cm mass attached to the uterine cervix and vaginal
wall was completely removed. The adnexa were normal. On section, the tumor
consisted of a large central cystic part and a solid part with peripheral
cystic hemorrhagic necrotic areas. No fat tissue was in the lesion.
Microscopically, the mass consisted of a thyroid tissue composed of multiple
follicles and stroma (Fig. 1D).
The final histologic diagnosis was pure struma of the uterus. No evidence of
malignant change was present in the struma uteri.
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Fig. 1D —35-year-old woman with pure struma of uterus. Microscopic
section shows mass consisted of thyroid tissue containing multiple follicles
filled with viscous colloid and abundant fibrous tissues.
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Discussion
It is rare for a primary teratoma to develop in the uterus. Teratomas of
the uterus have occurred in the uterine cavity, cervical canal, and uterine
surface [1,
2]. The lesions have occurred
in patients between the ages of 28 and 47 years old and have appeared as a
cystic mass or a solid mass with variably sized cysts
[1,
2,
4]. The majority of the tumors
were mature teratomas, and only two immature teratomas have been described
[1]. Two radiologic reports of
teratoma in the uterus have been described
[1,
2]. MRI and CT have been
reported to show a cystic tumor with fat tissue in mature teratoma
[2]. A solid mass with
scattered low-density areas and small foci of calcification has been reported
in an immature teratoma [1]. A
diagnosis of teratoma in the uterus cannot be made when imaging techniques do
not display the characteristic findings. If CT or MRI shows the presence of
fat tissue within a tumor in the uterus, the differential diagnosis might
include teratoma and lipoleiomyoma. We suggest that teratoma of the uterus can
be distinguished from lipoleiomyoma because teratoma tends to occur in
relatively young patients, in contrast to lipoleiomyoma, which tends to occur
in postmenopausal women
[5].
Neoplasm composed of struma is most commonly found in the ovary. Although a
struma salpingii and an ectopia consisting of thyroid and parathyroid tissue
in the vagina have been described
[1,
6], no reports can be found of
a thyroid tissue component in the uterus. In a limited number of past
radiologic reports with struma ovarii, the lesions were complex multilobulated
masses with thickened septa [7,
8]. The cystic components
showed low and high signal intensity on T1- and T2-weighted images. Some
cystic areas showed a characteristic appearance such as hyperintensity on
T1-weighted images and hypointensity on T2-weighted images. Histologically,
viscid fluid and viscid gelatinous materials are often observed in thyroid
follicles. This histologic characteristic accounts for hyperintensity on
T1-weighted images and hypointensity on T2-weighted images in the cystic
spaces of struma ovarii [8].
The MR signal intensity characteristics of solid portions were found to be
viable [7,
8]. As described, low signal
intensity areas on T2-weighted images represented stroma containing abundant
blood vessels and fibrous tissue in solid portions
[7]. As mentioned, struma
ovarii can have a variety of signal intensities in the cystic and solid
components. Thus, a specific diagnosis of struma ovarii is often difficult to
make. However, when spotty areas show hyperintensity on T1-weighted images or
hypointensity on T2-weighted images within the lesions, struma ovarii can be
considered with a high probability.
In the current case, we thought the lesion was a uterine leiomyoma with
hemorrhagic degenerations. On T2-weighted MR images, leiomyomas are
hypointense, similar to the pelvic muscles, with occasional hyperintense areas
corresponding to various degenerations. In this case, spotty areas showed
hyperintensity on T1-weighted images, and hypointensity on T2-weighted images
were further seen at the periphery of the lesion. These signal patterns have
commonly been seen with hemorrhagic materials or increased protein
concentration, although they are seen with several pathologic entities. Such a
relatively specific MR appearance might permit the prediction of viscid fluid
and viscid gelatinous materials within the mass and a diagnosis of struma
uteri. However, spotty areas with these intensities within the mass are also
seen in leiomyomas and leiomyosarcomas because these images are often observed
in the lesions. Thus, it was not easy to make the distinction. It is known
that struma ovarii often accumulate radioiodine, and a positive finding allows
a definite diagnosis [8]. In
the current case, radioiodine scintigraphy was not performed. When struma
uteri can be considered in the differential diagnosis of a mass by recognition
of spotty areas with hyperintensity on T1-weighted images and hypointensity on
T2-weighted images within the lesion, radioiodine scintigraphy should be
performed. If the mass accumulates radioiodine, a definite diagnosis of struma
uteri can be made.
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Introduction
Case Report
