A case of eosinophilic cystitis coexisting of superficial bladder cancer, mimicking muscle-invasive cancer.

Introduction: Here, we present a rare case of eosinophilic cystitis coexisting with bladder cancer, which appeared to be an invasive carcinoma on imaging. Case presentation: A 46-year-old man presented with urinary urgency. Computed tomography revealed an irregular and thickly enhanced bladder wall, which seemed to be invasive bladder cancer. Cystoscopy revealed a raspberry-like mass lesion on the entire bladder circumference. Pathological diagnosis after transurethral resection was pathological T1 urothelial carcinoma. After a thorough discussion of treatment options, the patient elected to receive intravesical Bacillus Calmette-Guérin. Three months after Bacillus Calmette-Guérin administration, no residual disease was confirmed by transurethral biopsy, and no recurrence was observed over 2 years. As peripheral eosinophilia and submucosa eosinophil infiltration were identified, the patient was diagnosed with coexisting eosinophilic cystitis and urothelial carcinoma. Conclusion: Clinicians should consider the possibility of eosinophilic cystitis with superficial bladder cancer coexistence in patients who present with an irregular and thick bladder wall.