Low grade transitional cell carcinoma and instrument artifact. A challenge in urinary cytology.

This was a retrospective study of 46 cases of urine specimens to distinguish low grade transitional cell carcinoma (TCC) and instrument artifact. The cytomorphologic features of 46 urinary specimens showing papillary fragments were studied. Urine from TCC showed papillary and irregular groups of cells with ragged borders and subtle nuclear changes. Urine after instrumentation showed cellular specimens with cohesive, ball-shaped and papillary clusters with smooth borders lined with a denser-staining cytoplasmic collar. The evenness of the border and presence of the cytoplasmic collar were distinguishing features of instrument artifact.