PATHOLOGY

Comparisons of outcome and prognostic features among histologic subtypes of renal cell carcinoma
Cheville JC, Lohse CM, Zincke H, Weaver AL, Blute ML
Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota 55905, USA
Am J Surg Pathol. 2003; 27: 612-24

• Our objective was to compare cancer-specific survival and to examine associations with outcome among the histologic subtypes of renal cell carcinoma (RCC). We studied 2385 patients whose first surgery between 1970 and 2000 was a radical nephrectomy for sporadic, unilateral RCC. All RCC tumors were classified following the 1997 Union Internationale Contre le Cancer and American Joint Committee on Cancer guidelines. There were 1985 (83.2%) patients with clear cell, 270 (11.3%) with papillary, 102 (4.3%) with chromophobe, 6 (0.3%) with collecting duct, 5 (0.3%) with purely sarcomatoid RCC and no underlying histologic subtype, and 17 (0.7%) with RCC, not otherwise specified. Cancer-specific survival rates at 5 years for patients with clear cell, papillary, and chromophobe RCC were 68.9%, 87.4%, and 86.7%, respectively. Patients with clear cell RCC had a poorer prognosis compared with patients with papillary and chromophobe RCC (p < 0.001). This difference in outcome was observed even after stratifying by 1997 tumor stage and nuclear grade. There was no significant difference in cancer-specific survival between patients with papillary and chromophobe RCC (p = 0.918). The 1997 TNM stage, tumor size, presence of a sarcomatoid component, and nuclear grade were significantly associated with death from clear cell, papillary, and chromophobe RCC. Histologic tumor necrosis was significantly associated with death from clear cell and chromophobe RCC, but not with death from papillary RCC. Our results demonstrate that there are significant differences in outcome and associations with outcome for the different histologic subtypes of RCC, highlighting the need for accurate subtyping.
  
• Editorial Comment
  Molecular genetics had an impact on classification of renal cell tumors. The genetic alterations affect the biology of the tumor cells, in respect of proliferation, cell death, differentiation, and cell adhesion; these very properties play a role in determining both the morphology and the behavior of tumors. Most of the pathologists use classifications of renal tumors based on cytomorphologic and genetic characteristics. According to the Heidelberg classification (J Pathol. 1997; 183: 131-3) and the 1997 workshop held in Rochester, Minnesota, USA (Cancer 1997; 80: 987-9) the clasification of renal cell tumors is based on these characteristics. The benign tumors are papillary adenoma (must have < 5mm in greatest diameter), oncocitoma and metanephric adenoma and the malignant tumors are conventional (clear cell) renal carcinoma, papillary renal carcinoma, chromophobe renal carcinoma, collecting duct carcinoma and unclassified cell carcinoma. Sarcomatoid carcinoma is not a particular tumor. Sarcomatoid change has been found to arise in all of the types of carcinoma in this classification, as well as in urothelial carcinoma of the renal pelvic mucosa.
  The paper of this editorial comment is a timely study to make valuable this classification for the urologists. The authors studied the prognostic features among the several histologic subtypes of renal cell carcinoma. Patients with clear cell renal cell carcinoma had a poorer prognosis compared with patients with papillary and chromophobe renal cell carcinoma with no significant difference in cancer-specific survival between patients with papillary and chromophobe renal cell carcinoma. The paper also disclosed the need and importance for reporting tumor size, sarcomatoid component, grading and tumor necrosis. Tumor size, presence of a sarcomatoid component, and nuclear grade were significantly asociated with death from clear cell, papillary, and chromophobe renal cell carcinoma. Histologic tumor necrosis was significantly associated with death from clear cell and chromophobe renal cell carcinoma, but not with death from papillary renal cell carcinoma.

Dr. Athanase Billis
Full-Professor of Pathology
State University of Campinas, Unicamp
Campinas, São Paulo, Brazil