Tumor grade appears to correlate significantly with the natural history of transitional cell carcinoma. The higher the grade of the diagnosis, the higher the incidence of death from the disease within two years. Invasive bladder tumors tend to spread rapidly to the regional lymph nodes and then into adjacent structures. Preneoplastic Lesions Damage to the urothelium caused by carcinogens, infection, stones, or catheters, may result in the permanent loss of the mature superficial cells and increase the rate of cell division in the basal layer, leading to the formation of hyperplastic urothelium of immature cells. The normal pattern of differentiation can easily be disturbed and give rise to various nonmalignant phenotypes, notably squamous or glandular metaplasia.
Most bladder carcinomas develop from a spectrum of preneoplastic and preinvasive urothelial disease.
Hyperplasia is defined as an increase in the number of cell layers without the loss of polarity, as well as nuclear crowding and the expression of various degrees of polymorphism. While some categorize atypical hyperplasia in varying degrees of severity, others use the term dysplasia, which is characterized by the loss of cellular polarity, nuclear crowding, granular chromatin, and small nucleoli. Severe dysplasia is often regarded as carcinoma in situ. Carcinoma in situ Carcinoma in situ is a flat, nonpapillary, noninvasive, histopathologically anaplastic epithelium. A localized lesion adjacent to a superficial papillary or an invasive tumor.