Cytologic manifestations of cystitis follicularis in urine specimens.

Four cases of cystitis follicularis diagnosed by urine cytology are presented, and are the first reported in the cytologic literature. Cystitis follicularis (follicular cystitis) is characterized by formation of lymphoid follicles in the lamina propria of the trigonal region of the bladder, and is considered to be the result of repeated bouts of urinary tract infection, usually bacterial, with other pathologic processes contributing to the development and prolongation of the infection. Cytologically it differs from chronic cystitis with prominent lymphocytosis by the presence of cellular elements from the germinal centers of lymphoid follicles, reminiscent of the cytologic findings in follicular cervicitis, with possible additional epithelial cytologic atypias from the overlying urothelium, which frequently undergoes reactive changes (hyperplastic, metaplastic, and ulcerative). The practical aspect of recognition of this entity in cytologic specimens is avoiding diagnostic errors of possible malignancy (lymphoid or other), and also of other forms of inflammatory disease, such as granulomatous type, with a different clinical significance.