carcinoma of the urinary bladder
Chapter: 17
A malignant tumor of the bladder epithelium. Most are histologically transitional cell carcinomas, which can be further classified (graded) as low grade (I), intermediate grade (II) and high grade (III) malignancies. The World Health Organization has proposed that transitional cell carcinomas be divided into 3 grades on the basis of urothelial architecture; cell size, pleomorphism, nuclear polarization, and hyperchromatism; and the number of mitoses present . Invasive carcinoma is often preceded by carcinoma in situ. Carcinoma in situ (CIS) is recognizable as flat, non-papillary anaplastic epithelium. The urothelium lacks the normal cellular polarity, and cells are large and have prominent nucleoli. In addition, exophytic lesions occurring with CIS are more likely to recur and invade. Tumors, especially those that are grade I and II, may be papillary and endophytic. Grade III tumors are usually exophytic and highly invasive. Squamous cell carcinomas account for 10% of tumors. These tumors are preceded by squamous metaplasia of the bladder epithelium and are an especially common complication of chronic inflammation in schistosomiasis. Adenocarcinomas are rare, and usually found in the dome of the bladder presumably arising from the remnants of the urachus
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