F-18 FDG PET/CT findings of a case of complete hydatidiform mole

Diagnostic Challenges in Invasive Mole With 18F-FDG PET/CT

ABSTRACT

A 34-year-old woman underwent 18F-FDG PET/CT scan following a diagnosis of an invasive mole. Although CT indicated multiple lung metastases, FDG uptakes were not evident. In contrast, FDG uptakes were observed in the pelvic lesion including the left ovary, suggestive of ovarian metastasis. MRI disclosed a ring-shaped enhancement typical of a corpus luteum. This corpus luteum was supposed to be maintained by the elevated human chorionic gonadotropin excreted from the invasive mole. This case underlines the importance of careful interpretation of 18F-FDG PET/CT in the evaluation of invasive moles, highlighting potential false positive in corpus luteum.

Imaging of Hepatic Ectopic Pregnancy by 18F-FDG PET/CT

Hepatic ectopic pregnancy is an uncommon form of extrauterine pregnancy. A 31-year-old woman had acute abdominal pain and distention. Laboratory examination showed significantly increased serum β-human chorionic gonadotropin level. Both ultrasound and MRI identified a lesion located at the right lobe of the liver. FDG PET/CT was performed to determine whether the other causes of elevated β-human chorionic gonadotropin level, which showed an oval mass with mid peripherally increased FDG activity. After surgery, pathological results confirmed a diagnosis of hepatic ectopic pregnancy.

Role of 18F-FDG PET in the management of gestational trophoblastic neoplasia

PURPOSE

Gestational trophoblastic neoplasia (GTN) is a rare and aggressive tumour that is usually sensitive to chemotherapy. The usefulness of conventional imaging modalities in evaluating treatment response is limited, mainly due to the difficulty in differentiating between residual tumour tissue and necrosis. The aim of the present study was to evaluate the role of FDG PET or PET/CT in primary staging and in monitoring treatment efficacy. The effect of FDG PET and combined PET/CT on the management of patients with GTN was also evaluated comparing the differences between standard treatments based on conventional imaging and alternative treatments based on PET.

METHODS

This retrospective study included 41 patients with GTN referred to San Raffaele Hospital between 2002 and 2010. All patients were studied by either PET or PET/CT in addition to conventional imaging. Of the 41 patients, 38 were evaluated for primary staging of GTN and 3 patients for chemotherapy resistance after first-line chemotherapy performed in other Institutions. To validate the PET data, PET and PET/CT findings were compared with those from conventional imaging, including transvaginal ultrasonography (TV-US) in those with uterine disease, CT and chest plain radiography in those with lung disease and whole-body CT in those with systemic metastases. Conventional imaging was considered positive for the presence of uterine disease and/or metastases when abnormal findings relating to GTN were reported. PET and PET/CT were considered concordant with conventional imaging when metabolic active disease was detected at the sites corresponding to the pathological findings on conventional imaging. In addition, in 12 of the 41 patients showing extrauterine disease, FDG PET/CT was repeated to monitor treatment efficacy, in 8 after normalization of beta human chorionic gonadotropin (βHCG) and in 4 with βHCG resistance. In some patients, PET or PET/CT findings led to an alternative nonconventional treatment, and this was considered a change in patient management for the study analysis.

RESULTS

When compared to TV-US, chest radiography and CT for staging, PET showed a concordance in 91 %, 84 % and 81 % of patients, respectively. In 8 of the 41 patients with extrauterine disease during staging, PET/CT showed a complete response to therapy after βHCG normalization. PET and PET/CT identified the sites of persistent disease in all seven high-risk patients with βHCG resistance, of whom four underwent second-line chemotherapy, two surgical removal of resistant disease instead of additional chemotherapy, and one surgical removal of resistant disease and second-line chemotherapy with subsequent negative βHCG.

CONCLUSION

In staging, PET cannot replace conventional imaging and does not show any information in addition to that shown by conventional imaging. The additional value of PET/CT in GTN with respect to conventional imaging is found in patients with high-risk disease. PET can identify the sites of primary and/or metastatic disease in patients with persistent high levels of βHCG after first-line chemotherapy and may be of additional value in patient management for guiding alternative treatment.