Bladder carcinoma.

β-naphthylamine. Cigarette smoking, chronic cystitis, schistosomiasis of the bladder, and certain drugs (cyclophosphamide)

Urothelial (transitional) cell carcinomas range from papillary to flat, noninvasive to invasive, and low grade to high grade. Low-grade carcinomas are always papillary and are rarely invasive, but they may recur after removal.

Increasing degrees of cellular atypia and anaplasia are encountered in papillary exophytic growths, accompanied by an increase in the size of the lesion and evidence of invasion of the submucosal or muscular layers

only 5% of bladder cancers are true squamous cell carcinomas

in situ stage of bladder carcinoma can be recognized, often in individuals with previous or simultaneous papillary or invasive tumors

The clinical significance of bladder tumors depends on their histologic grade and differentiation and, most importantly, on the depth of invasion of the lesion

Normal urothelium with uniform nuclei and well-developed umbrella cell layer. B, Flat carcinoma in situ with numerous cells having enlarged and pleomorphic nuclei

Four morphologic patterns of bladder tumors