What are the possible false positive and false negative findings on radiography for transitional cell carcinomas (TCCs)?

Updated: Mar 18, 2019
  • Author: Ali Nawaz Khan, MBBS, FRCS, FRCP, FRCR; Chief Editor: Eugene C Lin, MD  more...
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Calcification is seen in 10% of renal cell carcinomas. Retroperitoneal tumors, infections, or inflammation; pelvic tumors; pelvic lipomatosis; and gynecologic and gastrointestinal pathologies may cause extrinsic ureteric obstruction. Other causes of ureteric obstruction or bladder abnormalities include irradiation, surgery, trauma, or infections such as tuberculosis or schistosomiasis. These conditions may result in telltale signs on plain radiographs.

Other causes of filling defects may mimic a TCC, such as radiolucent or uric acid stones; blood clots; sloughed papilla caused by papillary necrosis; or fungal balls in patients with diabetes. Vessel crossing may cause a linear extrinsic impression; in these cases, oblique or compression images may help in differentiating TCCs from urothelial tumors. Tuberculosis can cause narrowing of the infundibulum and irregular calices. With regard to imaging, tuberculosis is the major disorder in the differential diagnosis.

Other mimics include pyeloureteritis cystica, renal cell carcinoma invading the pelvicaliceal system, or choleastoma. Squamous cell carcinoma (SCC) is radiographically indistinguishable from TCC; however, SCC is less likely to be a polypoid tumor. Although a diagnosis may be made on the basis of urograms or cystograms, a small bladder tumor, especially one of the infiltrative types, may go undetected. Furthermore, a dense concentration of contrast material may obscure the intraluminal part of the urothelial tumor.

Mimics of ureteric TCC include papilloma or polyp, which commonly produces a long, smooth intraluminal filling defect. This defect may prolapse up and down the ureter on serial images, and it may even intussuscept. Avoiding the introduction of air bubbles is important because these could be mistaken for tumors.

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