Non-Urothelial Malignancies and Other Miscellaneous Lesions

Non-Urothelial malignancies (NUM) are uncommon and make up less than 5% of bladder tumors. They refer to malignancies other than high-grade urothelial carcinomas (HGUC) and may present as primary or secondary disease. NUM can demonstrate epithelial or non-epithelial features and frequently pose diagnostic challenges for cytologists and pathologists, due to their morphologic overlap with HGUC.Primary epithelial NUM, including pure squamous cell carcinoma, adenocarcinoma, and small-cell carcinoma, have been shown to carry an aggressive biological behavior and often present at an advanced stage. Non-epithelial NUM include sarcoma, melanoma, and lymphoma. Secondary involvement of the urinary bladder by NUM occurs through metastases from distant sites or by direct extension from adjacent organs, such as the cervix, colorectum, and prostate.Urine cytology can be a helpful tool in the initial diagnosis of primary or secondary NUM, which can be critical for appropriate management and subsequent prognostication.