Pathology and terminology of interstitial cystitis/bladder pain syndrome: A review

Interstitial cystitis/bladder pain syndrome (IC/BPS) is an umbrella term of chronic debilitating conditions of unknown etiology characterized by symptoms of lower urinary tract hypersensitivity such as bladder pain/discomfort, urgency, and urinary frequency. The pathological features of IC/BPS have been generally reported as non-specific chronic inflammatory changes, with mast cell infiltration as a potential key finding. However, growing evidence reveals a histological distinction between IC/BPS with Hunner lesions and IC/BPS without Hunner lesions, and also sheds doubt on the diagnostic value of the mast cell count. Specifically, IC/BPS with Hunner lesions is an inflammatory disorder characterized by pancystitis with B cell abnormalities and epithelial denudation, while IC/BPS without Hunner lesions shows minimal histological changes. The umbrella term "IC/BPS" connects totally distinct clinical entities. Pathological evaluation thus plays an important role in the precise subtyping and clinical management of IC/BPS. In addition, terminology should be developed to refer separately to IC/BPS with Hunner lesions and IC/BPS without Hunner lesions.