Prognostic utility of the recently recommended histologic classification and revised TNM staging system of renal cell carcinoma - A Swiss experience with 588 tumors

BACKGROUND. A new, internationally accepted histologic classification of re nal cell carcinoma (RCC) and a new edition of the TNM staging system were i ntroduced in 1997. In the latter, there was a dramatic change in the pT cla ssification 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 w ere reevaluated to define morphologic prognostic parameters in RCC. pT clas sification (TTM 1997), histologic subtype, histologic tumor grade, presence of necrosis, and sarcomatoid differentiation were assessed. RESULTS. The histopathologic review according to the new classification rev ealed 487 conventional (clear cell) (83%), 64 papillary (11%), 31 chromopho be (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 n ot 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 sma ll cells (type 1] behaved less aggressively than papillary tumors with eosi nophilic cytoplasm and large cells [type 2; P < 0.001). CONCLUSIONS. Accurate histologic classification according to the new recomm endations has implications because the prognostic importance of other histo logic features that are of independent significance Varies with tumor subty pe. The data suggest that the new pT classification allows good separation of prognostic groups of patients Kith renal cancer. (C) 2000 American Cance r Society.