Background: A new, internationally accepted histologic classification of renal cell carcinoma (RCC) and a new edition of the TNM staging system were introduced in 1997. In the latter, there was a dramatic change in the pT classification of organ-confined renal cancer in which the break point between category pT1 and pT2 was increased from 2.5 cm to 7 cm.
Methods: To study the significance of the new pT classification and the new recommendations for histologic classification, 588 nephrectomy specimens were reevaluated to define morphologic prognostic parameters in RCC. pT classification (TNM 1997), histologic subtype, histologic tumor grade, presence of necrosis, and sarcomatoid differentiation were assessed.
Results: The histopathologic review according to the new classification revealed 487 conventional (clear cell) (83%), 64 papillary (11%), 31 chromophobe (5%), and 6 collecting duct (1%) RCCs. Clinical follow-up was available for 470 RCCs. The new pT classification (1997) was strongly correlated with patient survival (P < 0.0001). Histologic grade, presence of necrosis, and sarcomatoid differentiation provided independent prognostic information on the clear cell subtype of renal cancer. Sarcomatoid differentiation, but not tumor necrosis, portended a dismal prognosis for patients with papillary RCC. Chromophobe RCC was associated with a significantly better prognosis than clear cell RCC (P = 0.05). Papillary RCC with scanty cytoplasm and small cells (type 1) behaved less aggressively than papillary tumors with eosinophilic cytoplasm and large cells (type 2; P < 0.001).
Conclusions: Accurate histologic classification according to the new recommendations has implications because the prognostic importance of other histologic features that are of independent significance varies with tumor subtype. The data suggest that the new pT classification allows good separation of prognostic groups of patients with renal cancer.
Copyright 2000 American Cancer Society.