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“Soap bubble” sign as an imaging marker for posterior fossa ependymoma Group B

  • Diagnostic Neuroradiology
  • Published:
Neuroradiology Aims and scope Submit manuscript

Abstract

Purpose

To investigate the predictive value of the “soap bubble” sign on molecular subtypes (Group A [PFA] and Group B [PFB]) of posterior fossa ependymomas (PF-EPNs).

Methods

MRI scans of 227 PF-EPNs (internal retrospective discovery set) were evaluated by two independent neuroradiologists to assess the “soap bubble” sign, which was defined as clusters of cysts of various sizes that look like “soap bubbles” on T2-weighted images. Two independent cohorts (external validation set [n = 31] and prospective validation set [n = 27]) were collected to validate the “soap bubble” sign.

Results

Across three datasets, the “soap bubble” sign was observed in 21 PFB cases (7.4% [21/285] of PF-EPNs and 12.9% [21/163] of PFB); none in PFA. Analysis of the internal retrospective discovery set demonstrated substantial interrater agreement (1st Rating: κ = 0.71 [0.53–0.90], 2nd Rating: κ = 0.83 [0.68–0.98]) and intrarater agreement (Rater 1: κ = 0.73 [0.55–0.91], Rater 2: κ = 0.74 [0.55–0.92]) for the “soap bubble” sign; all 13 cases positive for the “soap bubble” sign were PFB (p = 0.002; positive predictive value [PPV] = 100%, negative predictive value [NPV] = 44%, sensitivity = 10%, specificity = 100%). The findings from the external validation set and the prospective validation set were similar, all cases positive for the “soap bubble” sign were PFB (p < 0.001; PPV = 100%).

Conclusion

The “soap bubble” sign represents a highly specific imaging marker for the PFB molecular subtype of PF-EPNs.

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Data Availability

Data could be made available to qualified researchers upon reasonable request and agreement of a data-transfer agreement by the corresponding author.

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Acknowledgements

We thank all the staff and patients in the participating centers for their contributions to this study.

Funding

This work was supported by the National Science Foundation of China (Nos. 81870958 and 81571631), the Beijing Municipal Natural Science Foundation for Distinguished Young Scholars (No. JQ20035), the Special Fund of the Pediatric Medical Coordinated Development Center of Beijing Hospitals Authority (No. XTYB201831).

Author information

Author notes

  1. Ying Jin and Dan Cheng contributed equally to this work.

Authors and Affiliations

  1. Department of Radiology, Beijing Tiantan Hospital, Capital Medical University, Beijing, 100070, China

    Ying Jin, Dan Cheng, Yunyun Duan, Zhizheng Zhuo, Tiantian Hua, Hongfang Li, Sven Haller & Yaou Liu

  2. Department of Medical Imaging Product, Neusoft, Group Ltd., Shenyang, 110179, China

    Jinyuan Weng

  3. Department of Radiology, Yantai Yuhuangding Hospital, Yantai, 264000, Shandong, China

    Chengzhou Zhang

  4. Department of Radiology, Sanbo Brain Hospital, Capital Medical University, Beijing, 100070, China

    Mingwang Zhu

  5. Department of Pathology, Beijing Tiantan Hospital, Capital Medical University, Beijing, 100070, China

    Xing Liu & Jiang Du

  6. CIMC-Centre d’Imagerie Médicale de Cornavin, Geneva, Switzerland

    Sven Haller

  7. Department of Surgical Sciences, Radiology, Uppsala University, Uppsala, Sweden

    Sven Haller

  8. Faculty of Medicine of the University of Geneva, Geneva, Switzerland

    Sven Haller

  9. Department of Radiology and Nuclear Medicine, Amsterdam UMC, Vrije Universiteit, Amsterdam, The Netherlands

    Frederik Barkhof

  10. Queen Square Institute of Neurology and Center for Medical Image Computing, University College London, London, UK

    Frederik Barkhof

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  1. Ying Jin
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Correspondence to Yaou Liu.

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Jin, Y., Cheng, D., Duan, Y. et al. “Soap bubble” sign as an imaging marker for posterior fossa ependymoma Group B. Neuroradiology 65, 1707–1714 (2023). https://doi.org/10.1007/s00234-023-03231-9

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  • DOI: https://doi.org/10.1007/s00234-023-03231-9

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