Variable penetrance of a consensus classification scheme for renal cell carcinoma

To evaluate the penetrance of the new pathologic standard of care, we characterized the temporal trends in histologic subtype-specific kidney cancer incidence rates. Molecular genetics have refined our understanding of kidney cancer, such that kidney cancer is now recognized as a family of tumors with distinct molecular and clinical characteristics. The histologic classification of kidney cancer has been revised to reflect this new paradigm.

Using the Surveillance, Epidemiology, and End Results Program, we identified incident cases from 1983 to 2002. Tumor histologic types were assigned, using the International Classification of Disease-Oncology codes. The histologic-specific incidence rates were calculated and directly age-adjusted to the 2000 U.S. population.

The histologic type was available for 40,813 cases. Subsequent to the Heidelberg consensus conference, the rate of papillary histologic types rose appropriately from 0.02 in 1998 to 0.89 in 2002 per 100,000 U.S. population, and the incidence of granular cell histologic types remained relatively stable (0.22 to 0.14 cases per 100,000), despite its exclusion as a unique histologic subtype. Paradoxically, the incidence of chromophobe tumors decreased during this interval (0.03 to 0.003 cases per 100,000).

Following the publication of the Heidelberg classification scheme, we have described the differential changes in incidence rates for newly described histologic variants. Our results suggest incomplete penetration of these guidelines. The continued reporting of granular cell histologic types is particularly noteworthy, given that it is no longer recognized as a distinct histologic subtype. Proper categorization of the histologic subtype (eg, chromophobe, papillary, clear cell) is imperative, because it may confer useful information regarding the prognosis, response to adjuvant treatment, and eligibility for clinical trials.