Mass Forming Eosinophilic Cystitis in Pediatric Patients.

Eosinophilic cystitis (EC) is an uncommon inflammatory disorder of uncertain etiology that has been described in adult and pediatric populations. We describe 3 recent cases of EC that presented as a mass lesion in pediatric patients from the New England region of the United States. All patients were initially suspected to have a malignancy, and biopsy was performed, which ultimately led to the diagnosis of EC. We propose the use of eosinophil density of >25 eosinophils per high-power field and myocyte degeneration as supportive histopathologic features to make this diagnosis. It is of utmost importance to consider EC in the differential diagnosis when approaching a pediatric patient with a bladder mass.