FDG-PET Findings in an Ovarian Endometrioma: A Case Report Jia-Huei Lin1, Victor Chit-kheng Kok2, Jian-Chiou Su3 1
Department of Nuclear medicine, Kuang Tien General Hospital, Sha-Lu, Taichung, Taiwan Division of Medical Oncology, Department of Internal Medicine, Kuang Tien General Hospital, Sha-Lu, Taichung, Taiwan 3 Division of General Surgery, Kuang Tien General Hospital, Sha-Lu, Taichung, Taiwan
2
Endometriosis is a common medical condition with rare
sound and magnetic resonance imaging (MRI), which may
reports of FDG findings in the scintigraphic literature.
identify larger endometriotic nodules of cysts. Laparoscopy
We present a 36-year-old premenopausal woman with
allows for definite confirmation an endometriosis diagnosis
a left ovarian endometrioma that presents a photopenic
as well as surgical treatment. 18F-fluorodeoxyglucose positron
defect on the FDG-PET scan. The case demonstrates
emission tomography (FDG-PET) scan, which reflects the
the value of FDG-PET scan in differentiating benign
amount of metabolism, are recently used to characteristize an
from malignancy in surveying ovarian lesions. The liter-
ovarian lesion in addition to other imaging modalities [5-8].
ature associated with endometriomas and FDG-PET
Herein we present a case with endometrioma and the FDG-
scan, and the factors that may contribute to FDG-PET
PET findings.
finding of endometriomas are discussed. Key words: FDG-PET, ovarian endometrioma, photopenic
Ann Nucl Med Sci 2008;21:109-113
Introduction Endometriosis is a common medical condition characterized by growth of tissue like endometrium beyond or outside the uterus [1-4]. Most endometriosis is found on structures in the pelvic cavity, including ovaries, fallopian tubes, the back and front of the uterus, uterine ligaments, intestines and urinay bladder. The common imaging tests are ultra-
Received 12/6/2007; revised 12/17/2007; accepted 12/25/2007. For correspondence and reprints contact: Jia-Huei Lin, M.D., Department of Nuclear medicine, Kuang Tien General Hospital. 117 Sha-Tien Road, Sha-Lu, Taichung 43303, Taiwan, ROC. Tel: (886)4-26625111ext. 2056, Fax: (886)426629167, E-mail address:
[email protected]
Case Report A 36-year-old premenopausal woman with a history of cesarean section had occasional lower abdominal tenderness occurring with her periods for 6 months. The pelvic ultrasound examination showed a left ovarian cyst about 5 cm in diameter without internal blood flow (Figure 1). Benign endometrioma was favored according to the findings of ultrasound. The CA125 level was elevated (48.19 unit/ml, reference range < 35.0 unit/ml). The alpha-fetal protein (AFP) level and beta-human chorionic gonadotrophin (beta-hCG) were within normal reference range. However, the patient required a self-pay FDG-PET to differentiate benign lesions from malignancies. The PET scan obtained one hour after intravenous injection of 11.3 mCi FDG revealed a photopenic area in the left posterior pelvis (Figure 2). Follow-up was suggested due the clinical benign impression. However, the lower abdominal tenderness with her period persisted for 2 months. Laparoscopy oophrocystectomy was thus suggested. Laparoscopy showed a left ovarian cyst with coffee fluid content. Left oophocystectomy was done and the pathology
ָڒዂ ඈ Lin JH et al
showed endometriosis. Left ovarian endometrioma was diagnosed. After surgery she underwent four courses of leuprorelin acetate depot followed by oral contraceptive pill. The symptoms of periodic lower abdominal tenderness remised during clinical follow-up for 8 months.
Figure 1. The ultrasound of gynecology shows a complex mass, about 68Ű45Ű50 mm in size, predominant cyst, in the left adnexa with no internal flow.
Discussion FDG-PET scan is well known with the value in differentiating benign from malignant lesions, for which the FDGPET scan was indicated in the present case. Ovarian endometriosis may present as a pelvis mass arising from growth of ectopic endometrial tissue within the ovary, so called ovarian endometrioma. Ovarian endometrioma sometimes have a solid nodule component due to focal endometrial tissue, which make it difficult to distinguish an endomerioma from the true solid tissue of a neoplasm. In three series studying patients with asymptomatic adenxal mass, the diagnostic performance of FDG-PET, MRI and transvaginal ultrasound were evaluated [5-7]. In differentiating benign
Figure 2. The FDG-PET scan shows a photopenic area (arrows) in the left posterior pelvis, corresponding to the left adenxal mass on the ultrasound. The focal FDG-accumulated areas surrounding the photopenic area disappears in the delayed image, probably due to physiologic bowel activity.
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Ӊ૰̄झ̰ቯሳFDG-PET FDG-PET findings in an ovarian endometrioma
from malignant asymptomatic adnexal mass, the sensitivity,
clear, two factors may contribute to the FDG uptake in
specificity and accuracy were 58%, 76% to 80% and 74% to
endomertiomas. First, the FDG uptake in the normal
77% for FDG-PET; 83%, 84% and 83% to 84% for MRI,
endometrial glands may be associated with the menstrual
and 92%, 59% to 60% and 63% to 64% for transvaginal
cycle. The endometrial gland may show FDG uptake espe-
ultrasound. Although combination of ultrasound with MRI
cially during menstrual flow phase and ovulatory phase [12-
and FDG-PET scan may improve accuracy, they pointed out
14]. Whether endometriomas would show FDG uptake dur-
that negative FDG-PET results do not rule out early-stage
ing those phases is not well understood. Since the
ovarian cancer or borderline malignancies. In Castellucci’s
endometriosis is defined as ectopic endometrial gland out-
study surveying 50 patients with pelvic lesions with FDG-
side the endometrial cavity and uterine musculature, it might
PET/CT and transvaginal ultrasound, the sensitivity, speci-
show FDG uptake as well as the endometrium of the uterus
ficity and accuracy was 87%, 100% and 92% for FDG-
in those phases [11]. Second, the endometriomas may show
PET/CT, and 90%, 61% and 80% for transvaginal ultra-
FDG uptake secondary to triggered inflammation [10].
sound. They concluded that FDG-PET/CT provides addition-
In conclusion, the ovarian endotrioma shows low FDG
al value to ultrasound for the differential diagnosis of benign
uptake in the present case. The FDG-PET scan offer impor-
from malignant pelvic lesions [8]. Although in the present
tant clinical information in survey an ovarian cystic lesion.
case the hypometabolic finding of the pelvis mass is consistent with the benign pathologic result of endometrioma, combination of clinical presentation with other imaging modality and histopathology are still required to make a precise diagnosis to avoid false-negative FDG-PET result in early-stage ovarian cancer or borderline malignancies. The ovaries are the first of the most common sites of endometriosis. Although ovarian endometrioma is not a rare disease, only few reports have mentioned its characteristics in FDG uptake. Holder et al [9] studied 103 FDG-PET scans of 76 patients with melanoma. One of them showed falsepositive PET scan due to endometriosis. Rieber et al [7] observed false-positive FDG PET results in 4 of 22 endometriomas in surveying 103 women with suspicious adnexal findings on ultrasound. In Fenchel’s study [5], 18 of 23 endometriomas did not show elevated FDG uptake while 5 did. In only one of the five cases the elevated FDG uptake could be clearly attributed to the tumor mass in the review of PET and MRI. Jeffry et al [10] reported a 32-year-old woman with left ovarian endometrioma and FDG uptake in the right paravesical area, assumed to be associated with inflammation rather to a cyst. Recently, Derman et al [11] reported a 47-year-old woman who had a pulmonary endometrioma with intense FDG uptake. Most of the reports in the literature demonstrate that the majority of endometriomas have low FDG metabolism with few exceptions. Although the exact mechanism is not
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