In an effort to characterize more fully multifocal renal cell carcinoma, 100 radical nephrectomy specimens with localized renal cell carcinoma were analyzed in a prospective fashion. Analysis of each specimen consisted of preoperative computerized tomography or magnetic resonance imaging, standard pathological examination with frozen section and 3 mm. step sectioning under magnification. Multifocal renal cell carcinoma was found in 16 specimens. Multifocal disease was suspected by preoperative imaging in 7 specimens (44%) and confirmed after standard pathological investigation in 10 (63%). Papillary and mixed histological patterns occurred at a significantly increased rate in specimens with multifocal disease (p = 0.011). Other parameters, such as stage, tumor size and volume, histological grade and deoxyribonucleic acid ploidy were evaluated and did not correlate with the presence or extent of multifocality. The number of secondary tumors per specimen varied from 1 to 50 (median 2) and were of higher grade in 3 (19%) and of lower grade in 2 (12%) when compared with the predominant tumor. In conclusion, information from preoperative and to some degree intraoperative tests (except histological pattern) cannot reliably predict multifocality. The true risk for unknown multifocality in a surgical setting seems to be 6%, which roughly corresponds to the incidence of locally recurrent disease in published large institutional series.
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