RESUMEN
OBJECTIVE: To describe cases of low grade papillary transitional cell carcinoma (LG-pTCC) with a low nuclear cytoplasmic (N/C) ratio and unusual cytologic patterns with many isolated, single neoplastic cells. STUDY DESIGN: We defined the following unusual cytologic findings as "isolated, single cell pattern": (1) numerous single cells sometimes with a few flat cell clusters; (2) very low N/C ratio; (3) angulation of cytoplasmic contour; (4) pale, homogeneous cytoplasm; (5) hyperchromatic nuclei with an uneven contour; (6) monotonous cytologic appearance; and (7) clear background. We studied 2,956 cytologic specimens of voided urine from 114 LG-pTCC patients at our university hospital during a 10-year period. RESULTS: Thirty-six specimens had the isolated, single cell pattern. The isolated, single cell pattern showed less celllular atypia than does the typical pattern of LG-pTCC. On histology the cases with the isolated, single cell pattern showed a papillary structure with an erosive surface and were composed of mildly atypical neoplastic cells with very low N/C ratios. CONCLUSION: Some LG-pTCCs show many single, atypical transitional cells.