Eosinophilic Cystitis Presenting as Possible Pediatric Rhabdomyosarcoma in Conventional Imaging Including ¹⁸F-FDG-PET/CT/MRI—A Rare Case

• Main Authors: Naja Enevold Olsen, Marie Øbro Fosbøl, Jorgen Thorup, Helle Hjorth Johannesen, Lise Borgwardt
• Format: Article
• Language: English
• Published: MDPI AG 2021-04-01
• Series: Diagnostics
• Subjects: eosinophilic cystitis; pediatric rhabdomyosarcoma; ¹⁸F-FDG-PET/CT/MRI; biomarker
• Online Access: https://www.mdpi.com/2075-4418/11/4/672

Eosinophilic cystitis (EC) is a relatively rare, but benign inflammatory bladder disease compared to that of the malignant pediatric rhabdomyosarcoma (RMS), in which it can be mimicking on initial suspicion. The origin, symptoms and findings of both EC and RMS are still discussed and hence, lead to the challenge in distinguishing them by cystoscopy and several image modalities. We present a case in which cross-sectional imaging modalities including fluorine-18-fluro-2-deoxy-D-glucose (¹⁸F-FDG)-positron emission tomography (PET) / computed tomography (CT) / magnetic resonance imaging (MRI) (¹⁸F-FDG-PET/CT/MRI (The imaging modality ¹⁸F-FDG-PET/CT/MRI referring to two continuous scans scanned on the same ¹⁸F-FDG-tracer dose for both the whole-body ¹⁸F-FDG-PET/CT and the regional ¹⁸F-FDG-PET/MRI of the pelvis.)) raised suspicion of RMS. Hence, the final diagnosis of EC was established by repeated histopathology. It is important to have EC in mind when seeking differential diagnosis of malignant diseases like RMS in order to provide the correct treatment for the patient and highly homogenously increased ¹⁸F-FDG-uptake should raise the suspicion of EC as a differential diagnosis. Furthermore, ¹⁸F-FDG-uptake rate is suggested as a future potential biomarker for monitoring of therapeutic response in eosinophilic inflammatory diseases, thus more research on this topic is needed.