Malignant tumour of the cells that cover and line the kidney. It usually affects persons over age 50 who have vascular disorders of the kidneys. It seldom causes pain, unless it is advanced. It may metastasize to other organs (e.g., lungs, liver, brain, bone) and go unrecognized until these secondary tumours cause symptoms. Blood can appear in the urine early on but is painless and usually disregarded. Even when the cancer is in the early stages, X-ray films can show deformity in kidney structures.
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Carcinoma in situ (CIS) is a pre-malignant condition, in which some cytological signs of malignancy are present, but there is no histological evidence of invasion through the epithelial basement membrane.
Carcinomas, like all cancers, are staged according to the extent of disease. The UICC/AJCC TNM system is often used, however for some common tumors, classic staging methods (such as the Dukes classification for colon cancer) are still used.