Benign Glandular Lesions of the Urinary Bladder: Diagnostic Criteria and Differential Diagnosis Considerations

Context.—: The urinary bladder is a unique organ that may be involved by both benign and malignant glandular lesions. Urothelial carcinoma may possess glandular differentiation, and other glandular malignancies may arise from or secondarily involve the urinary bladder. However, many benign glandular lesions may also involve the urinary bladder, and these can mimic malignancy. Relatively common benign lesions of the urinary bladder that may demonstrate glandular or tubular features include cystitis glandularis, glandular metaplasia, nephrogenic adenoma, Müllerian lesions, prostatic-type polyp, urachal remnant, and pseudocarcinomatous hyperplasia. Objective.—: To provide an overview of the various benign glandular lesions of the urinary bladder, with a focus on clinical and morphologic features, as well as potential ancillary studies (eg, immunohistochemistry) to distinguish them from malignant entities. Data Sources.—: Relevant medical literature indexed on PubMed and personal experiences of the senior authors. Conclusions.—: Benign glandular lesions of the urinary bladder typically do not possess high-grade cytologic atypia, frequent mitotic figures, or necrosis. However, diagnostic pitfalls exist for benign lesions with mild-to-moderate cytologic atypia, pseudoinfiltrative growth pattern, or architectural features that mimic malignancy. Being aware of the potential diagnostic pitfalls will help us to not mistake these benign glandular lesions for a malignant process.