Pitfalls in Urinary Tract Cytopathology

<b><i>Background:</i></b> Urine cytopathology is a cost-effective method to diagnose and follow patients with high-grade urothelial carcinoma (UC). However, some benign, reactive, and metaplastic changes may mimic UC and pose a diagnostic challenge for cytopathologists. <b><i>Summary:</i></b> Our comprehensive review focuses on summarizing common pitfalls encountered in urine cytopathology, based on the 2nd edition of The Paris System (TPS) for reporting urinary tract cytopathology and other recent published literature. These pitfalls include urothelial tissue fragments, degenerative changes, treatment effects, viral cytopathic changes, iatrogenic and metaplastic changes. Our aim was to provide a clear understanding of these mimics in order to avoid diagnostic errors. <b><i>Key Message:</i></b> It is crucial for cytopathologists to recognize benign, reactive, or metaplastic lesions that sometimes resemble UC. An awareness of these cytological changes is essential to make an accurate diagnosis.