Papillary and inverted tumors

Papillary neoplasms are a group of characteristic lesions of the urinary bladder, ranging from benign growths to malignant tumors. Papillary and inverted growth features can be identified grossly and microscopically. The classification of papillary neoplasms based on the new World Health Organization/International Society of Urological Pathology (WHO/ISUP) grading system is widely applied, although interobserver agreement varies, particularly with low-grade lesions. Differentiating high-grade urothelial carcinoma with inverted growth patterns from noninvasive inverted tumors is important, and neoplastic papillary lesions should be differentiated from reactive papillary changes. Papillary neoplasms are often treated by transurethral resection either with or without intravesical therapy, and accurate pathological assessment of these lesions plays a key role in the clinical management of patients.