Chromophobe renal cell carcinoma: a clinicopathologic study of 203 tumors in 200 patients with primary resection at a single institution.

Despite multiple studies, many clinicopathologic issues about chromophobe renal cell carcinoma (RCC) remain contentious; for example, its biological behavior-whether better or similar to papillary RCC, the incidence of sarcomatoid features, and whether pathologic features such as necrosis, nuclear grade, and tumor stage predict worse outcome. We studied 203 consecutive primary chromophobe RCCs resected at our institution in an attempt to answer these and other questions. The tumors showed significant progressive decrease in size and stage (P=0.047 and 0.001) from 1980 to 2000. Five patients had metastasis at presentation, and further disease-specific events (recurrence/metastasis/death due to disease) occurred in 8 more. Only 4 of 203 tumors had sarcomatoid features. Over median follow-up of 6.1 years (range, 0.1 to 18 y), 5-year and 10-year disease-specific events occurred in 3.7% (95% CI, 1.5%, 7.4%) and 6.4% (95% CI, 2.7%, 12.2%) patients. Outcomes showed significant association with tumor size, small-vessel invasion, sarcomatoid features, and microscopic necrosis (P≤0.05 each). pT stage or nodal metastasis tended to show some association, without reaching statistical significance (P=0.05 and 0.06, respectively). A modified tumor grading scheme, somewhat similar to that proposed recently, mitotic index, cytologic eosinophilia, and architecture, were not significantly associated with outcome. In conclusion, sarcomatoid differentiation is quite uncommon in chromophobe RCC. Tumor size, small-vessel invasion, sarcomatoid differentiation, and microscopic necrosis are the only features that are significantly associated with adverse outcome. On the basis of this long follow-up on a large number of cases, chromophobes seem to have better clinical outcomes than those reported for clear cell and papillary RCCs.