Morphology
Macroscopically tumor is a variegated appearance with yellowish areas, other white, necrotic, others red or hemorrhagic cystic areas and other hyaline or involution. The tumor compresses and infiltrates the renal tissue, the excretory system of the urinary tract, and often invades the veins, lymphatics, capsule and renal cell.
Microscopically the tumor is solid forms, tubular, or papillary cordonal and consists of large polygonal cells, limits net central core of cytoplasm relatively small and light (for the extraction of lipids and glycogen to make up). Cells and their arrangement are similar to those of a plant tissue. There are other less common cell types, such as chromophobe cells and cells fusadas, the latter can simulate a sarcoma. To establish the prognosis is necessary to evaluate the histologic grade: group 1 are better differentiated and less atypia, those in group 3, the worst differentiated, the latter are highly pleomorphic or sarcomatoid forms.
Metastases occur most frequently in skin, bone, lungs, central nervous system, liver and lymph nodes. At the time of nephrectomy prognostic value Robson classification into 4 stages.
Robson stages:
1: tumor confined to the kidney, no invasion of capsule, vein or pelvicalyceal apparatus;
2: invasion of the perirenal cell;
3: invasion of the renal vein, vena cava or regional lymph node metastases;
4: distant metastasis or invasion of adjacent organs (adrenal glands, spine).