I n their report, Albers et al. 1 present data on the potential clinical utility of immunohistochemical expression of Ki-67 in clinical Stage I nonseminomatous testicular germ cell tumors (NSGCT) to predict a group of patients at low risk for occult metastatic disease. Using a cutoff value of Γ΅70% MIB-1 positive nuclei, a negative predictive value of 88% was achieved and 30 of 34 clinical Stage I patients were correctly classified as pathologic Stage I. Using a cutoff value of 50% embryonal carcinoma (EC), the authors achieved a negative predictive value of 83% and 30 of 36 clinical Stage I patients were correctly classified as pathologic Stage I; the absence of vascular invasion was found in 38 of 46 clinical Stage I patients and pathologic Stage I disease was correctly predicted in 83% of the patients. The authors claim MIB-1 analysis is the best parameter for predicting low risk compared with histopathologic parameters by multivariate analysis. Based on their data, the authors state that MIB-1 staining produces reliable and reproducible results and state that it is justified to add MIB-1 analysis to the known histopathologic parameters to define patients at low risk for metastasis.