PET-CT findings in surgically transposed ovaries

18 F-FDG PET/CT Findings of Surgically Transposed Ovaries After Radical Hysterectomy in a Young Adult Patient

ABSTRACT

A 35-year-old woman underwent 18 F-FDG PET/CT 2 months after a radical hysterectomy for uterine cervical cancer. An apparent FDG uptake was observed in an oval-shaped mass with an attached surgical clip in the right paracolic gutter. A similar non-FDG-avid mass with a clip was observed in the left. In this case, ovarian transposition had also been performed with metallic clips placed on both sides of the paracolic gutters. The increased FDG uptake in the right paracolic gutter was interpreted as physiological uptake in the right transposed ovary, not metastasis. Recognizing the possibility of FDG uptake in transposed ovaries is important.

Characteristics of surgically transposed ovaries on 18F-FDG PET/CT among patients with cancer

OBJECTIVE

Fertility preservation in women with cancer is important for improving their quality of life. Successful ovarian transposition protects the ovary from radiation and preserves ovarian endocrine function and fertility. With the increasing use of 18F-FDG PET/CT in gynecologic malignancies, the findings of transposed ovaries sometimes vary. This study aimed to characterize the 18F-FDG PET/CT findings of surgically transposed ovaries among a large number of patients with various medical conditions.

METHODS

We retrospectively reviewed the medical records, including surgical history, and analyzed the findings of the transposed ovaries of patients who underwent ovarian transposition. Quantitative analysis was performed, and the maximum standardized uptake values (SUVs) were recorded. The Hounsfield unit (HU) and size (measured using the long diameter on the axial image) of the transposed ovary were evaluated.

RESULTS

No significant change was found in the SUV of the transposed ovaries in relation to age and time after surgery. In two cases in which metastasis occurred in the transposed ovary, the lesions showed higher SUVs and HUs than did the other non-metastatic transposed ovaries. In several serial follow-up cases, varying 18F-FDG uptake was observed.

CONCLUSION

The 18F-FDG uptake pattern of the transposed ovary did not differ from that of the normal ovary. Misinterpretation should be avoided by considering surgical records, presence of surgical clips, and patients' disease state. If there is a high uptake in the transposed ovary, it is necessary to check for soft tissue lesions and differentiate metastasis from the physiologic uptake.

PET/CT Variants and Pitfalls in Gynecological Cancers

The role of hybrid imaging with 2-[18F] flourodeoxyglucose (FDG) positron emission tomography and computed tomography (PET/CT) is continuously evolving and now considered standard practice in evaluation of disease stage, treatment response, recurrent disease and follow-up for numerous primary malignancies. In gynecological malignancies FDG PET/CT plays an important role, not only in the assessment of disease in the pre-and post-therapy setting, but also in radiation therapy (RT) planning by defining the metabolically active gross tumor volume (GTV. The glucose analogue radiotracer, FDG, is by far the most utilized radiotracer in PET/CT and is typically seen with high uptake in malignant cells. The radiotracer FDG has a high sensitivity but low specificity for malignancy, as benign processes with an inflammatory response for example infection, are also FDG-avid. In the evaluation of the female pelvic region an awareness of potential confounding factors in the interpretation of FDG is essential as variations of FDG uptake occur in accordance with the menstrual cycle and the menopausal state. Incidental imaging findings in the female genital can pose differential diagnostic challenges as false-positive and false-negative findings in benign and malignant processes are not uncommon. Gynecological malignancies continue to pose major public health problems with cervical cancer as the fourth most common cancer in women ranking after breast cancer, colorectal cancer and lung cancer. Familiarity with frequently encountered benign and malignant variants and pitfalls in FDG PET/CT in the female pelvic region can aid the reader in differential diagnostic considerations.

Physiologic uptake of 18F-FDG in transposed ovaries may mimic metastasis on 18F-FDG PET/CT imaging

BACKGROUND

Ovarian transposition is aimed at preserving ovarian function before irradiation in pelvic malignancies. The extrapelvic location of the ovaries and their physiologic fluorine-18-fluorodeoxyglucose (F-FDG)-uptake is a potential source of misdiagnosis as metastasis on F-FDG PET/CT. We describe the F-FDG PET/CT characteristics of transposed ovaries and their changes over time.

PATIENTS AND METHODS

We reviewed F-FDG PET/CT studies of all consecutive women with pelvic malignancies who underwent ovarian transposition between 2007 and 2013. Studies were grouped according to the time period over which they were carried out. Findings were categorized by location, size, appearance (solid/mixed/cystic), presence of surgical clips, ovarian F-FDG uptake (maximum standardized uptake value), and attenuation values on CT (Hounsfield units). Group time-period differences were assessed.

RESULTS

Seventy-nine F-FDG PET/CT studies were reviewed, 30 before and 49 after transposition. Time-period groups after transposition were up to 4 months (18 studies), 4.1-12 months (n=14), and more than 12 months (n=17). After transposition, ovaries were located mainly in the paracolic gutter (n=32) and subhepatic regions (n=18). Surgical clips were present in 67%. Both ovaries appeared more solid 1 year after surgery than preoperatively (13.7% before vs. 61.3% after surgery; P<0.001). Transient F-FDG-avidity was observed in 11 ovaries. Hounsfield unit values were higher within 4 months after surgery than preoperatively, reverting thereafter to preoperative values.

CONCLUSION

After ovarian transposition, nonanatomic location, loss of cysts formation in favor of solid appearance over time, and intermittent F-FDG uptake of functioning transposed ovaries might mimic metastatic lesions. Careful interpretation of F-FDG PET/CT findings is mandatory in women with pelvic malignancies who have undergone ovarian transposition.