A case report of Meigs’ syndrome: the ¹⁸F-FDG and ¹⁸F-FAPI PET/CT findings

Introduction

Meigs’ syndrome is characterized by the triad of benign ovarian fibroma or fibroma-like tumors, ascites, and pleural effusion, with resolution after tumor removal (1). Despite its benign nature, it often mimics ovarian malignancy due to similar imaging findings and elevated tumor markers such as cancer antigen 125 (CA-125) (2,3). ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) is commonly used for evaluating adnexal masses, however, FDG uptake may overlap between benign fibrous tumors and low-grade malignancies, limiting its diagnostic specificity (4,5). Fibroblast activation protein inhibitor (FAPI) is a novel molecular imaging tracer targeting fibroblast activation protein and has shown promising performance in oncologic imaging because of low physiologic background uptake and high lesion contrast (6-8).

However, the imaging characteristics of FAPI PET/CT in Meigs’ syndrome remain poorly defined. Limited reports suggest that FAPI uptake in ovarian fibrous tumors may be heterogeneous (9). Here, we report a case of Meigs’ syndrome with discordant dual-tracer PET/CT findings and discuss the potential interpretive value of combining ¹⁸F-FDG and ¹⁸F-FAPI imaging in this diagnostically challenging condition. We present this article in accordance with the CARE reporting checklist (available at https://rx.amegroups.com/article/view/10.21037/rx-26-0021/rc).

Case presentation

A 54-year-old postmenopausal woman presented with progressive dyspnea for one month. She had no remarkable past medical history or regular medication use. Short-term glucocorticoid nebulization after admission did not provide significant symptomatic relief. Chest and abdominal CT revealed massive right pleural effusion, ascites, and a 9.0 cm × 9.1 cm mixed solid-cystic pelvic mass (Figure 1). Laboratory tests revealed markedly elevated CA-125 (807.9 U/mL; normal, <35 U/mL) and human epididymis protein 4 (HE-4) (103.9 pmol/L; normal, <76.2 pmol/L) levels. Cytologic examination of the ascitic fluid showed a moderate number of mesothelial cells and lymphocytes, with no evidence of malignant cells. As shown in Figure 2, ¹⁸F-FDG PET/CT demonstrated mildly increased heterogeneous FDG uptake within the pelvic mass [maximum standardized uptake value (SUVmax), 4.64], while no other hypermetabolic lesions were identified. Because malignancy could not be excluded, ¹⁸F-FAPI PET/CT was performed under an institutional review board-approved clinical trial (No. 24429). Notably, the pelvic mass showed no discernible FAPI uptake. Because malignancy could not be confidently excluded preoperatively, the patient subsequently underwent total hysterectomy with bilateral adnexectomy. Histopathological examination confirmed a benign ovarian fibroma (Figure 3). The patient recovered uneventfully after surgery. At follow-up, the pleural effusion and ascites had resolved completely, and the tumor marker levels had returned to normal. No adverse or unanticipated postoperative events were documented in the available follow-up records. The major clinical events of the present case are summarized in Table 1. All procedures performed in this study were in accordance with the ethical standards of the institutional committee(s) and with the Declaration of Helsinki and its subsequent amendments. The study was approved by the Ethics Committee of The Third Xiangya Hospital. Written informed consent was obtained from the patient for the publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Figure 1 CT imaging findings at presentation. (A) Pelvic CT revealed a mixed solid-cystic pelvic mass (arrow). (B) Chest CT showed massive right pleural effusion (arrow). (C) Abdominal CT showed a small amount of ascites (arrow). CT, computed tomography.

Figure 2 The ¹⁸F-FDG and ¹⁸F-FAPI PET/CT imaging of the patient with Meigs’ syndrome. (A-D) ¹⁸F-FDG PET/CT images showed mildly increased heterogeneous FDG uptake in the pelvic mass on the MIP image (A, red arrow) and axial PET (B), CT (C), and fused PET/CT (D) images (white arrows; SUVmax, 4.64). (E-H) 18F-FAPI PET/CT images demonstrate no discernible tracer uptake in the pelvic mass on the MIP image (E, red arrow) and axial PET (F), CT (G), and fused PET/CT (H) images (white arrows; SUVmax, 1.8). CT, computed tomography; FAPI, fibroblast activation protein inhibitor; FDG, fluorodeoxyglucose; MIP, maximum intensity projection; PET, positron emission tomography; SUVmax, maximum standardized uptake value.

Figure 3 Histopathological findings of the resected ovarian mass. Microscopic examination showed a benign ovarian fibroma composed of spindle-shaped fibroblastic cells without cytologic atypia or malignant features (hematoxylin and eosin staining, ×200).

Discussion

Meigs’ syndrome is a rare benign entity that often mimics ovarian malignancy because of overlapping clinical presentation, imaging findings, and elevated tumor markers (3,10). In this case, a pelvic mass accompanied by ascites, pleural effusion, and markedly increased CA-125 and HE-4 levels initially suggested ovarian cancer. Mildly increased heterogeneous uptake on ¹⁸F-FDG PET/CT could not exclude a low-grade malignancy. In contrast, ¹⁸F-FAPI PET/CT demonstrated no tracer uptake in the lesion. Compared with a previously reported case of ovarian fibroma-associated Meigs’ syndrome showing mildly increased FAPI uptake, the present case showed essentially absent FAPI uptake, suggesting that FAPI findings in ovarian fibrous tumors may differ between cases (9).

A major strength of the present case is the availability of dual-tracer imaging with both ¹⁸F-FDG and ¹⁸F-FAPI PET/CT, together with histopathological confirmation and clear postoperative resolution of pleural effusion, ascites, and tumor marker abnormalities. This allowed direct comparison between metabolic and fibroblast-targeted imaging in a clinically equivocal adnexal mass. However, this report is limited by its single-case nature, the non-specificity of ¹⁸F-FAPI uptake, and the still limited literature in this setting. Therefore, the present findings should be interpreted with caution.

Tumor markers alone are insufficient for distinguishing benign from malignant disease in this setting. CA-125 may increase in benign conditions associated with peritoneal or pleural irritation, and HE-4, although relatively more specific, should still be interpreted in conjunction with imaging findings (3,11,12). The imaging pattern observed in this patient may reflect the limited metabolic activity of a benign fibrous tumor, resulting in only mild FDG uptake. The absence of FAPI uptake may indicate relatively low fibroblast activation or low tracer-accessible FAP expression within the lesion.

This case highlights the potential complementary value of dual-tracer PET imaging in evaluating adnexal masses with equivocal findings. Nevertheless, FAPI uptake is not specific for malignancy and may also occur in benign fibroinflammatory conditions (8,13). Thus, both positive and negative FAPI findings should be interpreted cautiously, and in combination with morphologic imaging, tumor markers, and clinical context.

In this patient, mild FDG uptake reflects the low metabolic rate of a benign fibrous tumor, mimicking low-grade malignancy (4,5). The lack of FAPI uptake further indicates minimal fibroblast activation or low FAP expression. However, absent FAPI uptake is not a standalone indicator of benignity (8,9). This case highlights that discordant dual-tracer imaging, interpreted alongside morphology and clinical markers, offers superior diagnostic clarity. While FAPI-PET shows promise as an adjunct for equivocal adnexal masses, larger studies are required to establish its definitive role in differentiating ovarian tumors (13).

Conclusions

This case demonstrates discordant ¹⁸F-FDG and ¹⁸F-FAPI PET findings in Meigs’ syndrome. Dual-tracer imaging may provide complementary information but is insufficient alone to differentiate benign from malignant ovarian tumors. Further evidence is required to clarify the diagnostic role of FAPI-PET in adnexal masses.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the CARE reporting checklist. Available at https://rx.amegroups.com/article/view/10.21037/rx-26-0021/rc

Peer Review File: Available at https://rx.amegroups.com/article/view/10.21037/rx-26-0021/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://rx.amegroups.com/article/view/10.21037/rx-26-0021/coif). M.Z. serves as an unpaid Associate Editor-in-Chief of Radiology-X from February 2026 to January 2028. The other authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the ethical standards of the institutional committee(s) and with the Declaration of Helsinki and its subsequent amendments. The study was approved by the Ethics Committee of The Third Xiangya Hospital. Written informed consent was obtained from the patient for the publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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