Follicular cystitis in urine cytology: A clinical and cytopathologic study.

Despite being an important differential diagnosis of bladder tumor on cystoscopy, follicular cystitis (FC) is rarely diagnosed on cytologic material. We performed a retrospective study on cases of FC diagnosed on bladder biopsy and/or urine cytology in our institution. A total of 35 cases of FC were identified with a female predominance (F:M = 2:1). Hematuria was the most common clinical presentation. Cystoscopic findings included mass lesions, yellow plaques, and surface erythema. History of urinary tract infection was reported in 48% of the patients, and majority of those patients had positive concurrent urine culture, most commonly with beta-hemolytic streptococcus, Group B. A total of 17 out of 35 patients had urine cytology specimens. When the presence of follicular dendritic cells in clusters of variously sized lymphocytes is used as the cytological diagnostic criterion, 6 out of 17 cases were diagnosed as FC and 5 out of 6 were confirmed by concurrent biopsy. This retrospective study not only analyzed the clinical characteristics of FC but also elucidated the cytological diagnostic criteria of FC and confirmed its specificity.