Assessment of Histopathological Parameters Useful in the Diagnosis of Low Grade Non-Invasive Urothelial Carcinomas.

Urothelial papillary lesions of urinary bladder are frequent lesions in medical practice and sometimes difficult to be histopathologically classified. In this study were included 179 urothelial papillary lesions, represented by low grade non-invasive urothelial carcinomas (LGNIUC), papillary urothelial neoplasms of low malignant potential (PUNLMP) and urothelial papillomas (UP), for which the architectural and cytological histopathological parameters were analyzed in order to determine their usefulness for the classification of lesions. For each parameter, an aggressivity score was set, the sum representing the composite histological score (CHS) for each case. The increase of urothelial thickness, the papillae fusion, the loss of cellular polarity, loss of basal cell palisading and absence of umbelliform cells were commonly associated with diffuse pattern in LGNIUC, were focal/absent in PUNLMP and absent in UP. The nuclear hypertrophy and hyperchromasia, the nucleoli presence and mitotic activity were specific for LGNIUC, rarely associated with PUNLMP and absent/low in UP. CHS values for the three categories of analyzed lesions were superior statistically significant in LGNIUC compared to PUNLMP and UP. The mitotic index and the thickness of cytological atypical epithelial layers support the parameters utility as reproducible criteria for the differentiation of papillary urothelial tumors.