Transitional cell neoplasms of the urinary bladder. Can biologic potential be predicted from histologic grading?

The concept that most transitional cell neoplasms of the urinary bladder exist as either nonaggressive lesions of low cytologic grade or aggressive anaplastic cancers is gradually gaining acceptance. The extent to which the biological potential of these neoplasms is revealed in their pathologic features is the subject of this article. Using guidelines developed in experimental models, a series of 400 transitional cell neoplasms selected for long-term follow-up were classified into the WHO system. The results indicate that (1) almost all transitional cell tumors can be grouped into low and high grades at initial presentation; (2) the low grade lesions (usually designated transitional cell carcinoma, Grade I) are benign and should be called papillomas rather than carcinomas; (3) the risk of progression is not a function of the number of recurrences for these noninvasive, low-grade, papillary tumors; (4) the high-grade neoplasms are aggressive whether papillary or nodular and account for greater than 93% of tumor-related deaths; (5) patients with high-grade lesions have a reduced life expectancy even if progression does not occur; (6) depth of invasion and growth pattern are limited as predictive factors compared with histologic grade; (7) histologic grading of the initial tumor tissue can be highly predictive of outcome.