Pathology of renal cancer and its metastases.

The pretherapeutic classification of renal carcinomas includes the assessment of the tumor stage, the histological gross pattern, the cytological features, and the histopathological grading. As to the local tumor extension the perinephric invasion and renal vein involvement are the most important prognostic features. The presence of metastases dramatically alters survival. Histologically, compact, tubular, and papillary growth patterns are differentiated. Furthermore, the verification of the cell types in renal carcinomas is of prognostic significance. The clear cell carcinomas are opposed to the granular cell and spindle-shaped/pleomorphic types with poor prognosis. Rarely tumors consist of so-called "chromophobe" cells with finely reticular cytoplasms. They closely resemble clear cell carcinomas and exhibit a similar biological behaviour. According to the grade of atypia in renal carcinomas three grades of malignancy are distinguished. Conclusively, the tumor grade and the tumor cell type are the most reliable indicators of the malignant potential of renal carcinomas.