Histologic tumor growth pattern is significantly associated with disease-related survival in muscle-invasive transitional cell carcinoma of the urinary bladder.

Tumor stage and lymph node status are currently the most established prognostic factors in muscle-invasive bladder cancer. However, there is still a need for new parameters allowing to assess the prognosis more accurately. A recently introduced morphologic classification of tumor growth, which distinguishes three growth patterns (nodular, trabecular, and infiltrative type), was retrospectively applied to a collective of 153 muscle-invasive bladder carcinomas in order to examine its prognostic relevance. Nodular pattern was found in 34 cases (22%), trabecular pattern in 97 cases (63%) and infiltrative pattern in 22 cases (14%) as the dominant type of tumor growth. The majority of cases (54%) displayed more than one tumor growth pattern. A two-tiered classification considering the worst type of tumor growth (non-infiltrative or infiltrative type) yielded 74 non-infiltrative tumors (55%) and 69 infiltrative tumors (45%). The former group was associated with a significantly better disease-related survival than the latter (p=0.007 by univariate Cox regression analysis). Moreover, the two-tiered classification was identified, besides tumor stage (p=0.036) and lymph node status (p=0.0001), as an independent predictor of disease-related survival in a multivariate analysis (p=0.029). In conclusion, our data suggest that the morphologic pattern of tumor growth is significantly associated with the clinical course of advanced transitional cell carcinomas of the bladder. The tumor growth classification proposed here may serve as an additional tool to predict the prognosis of patients undergoing radical cystectomy for bladder cancer.