390 Background: Cancer is a heterogeneous disease. Studying cancer heterogeneity may enable us to elucidate the various subtypes of a particular cancer, and improve the diagnosis, prognostication, and therapy of cancer. Nonseminomatous germ cell tumor (NSGCT) is a prime example of a heterogeneous disease. We determined potential lethality of NSGCT by characterizing the histological makeup of primary testicular tumors, the tumor burden, psychosocial issues, and surgical factors. Methods: From November 1997 to October 2012, 142 consecutive patients diagnosed with a NSGCT of the testis were evaluated for this study. The log-rank test was used to identify prognostic factors in univariate Kaplan-Meier analysis. A multivariate Cox regression model was used to evaluate predictive factors for overall survival. Results: Patient and tumor characteristics: median (range) age 25 (12 to 53); pathology – embryonal carcinoma 15%, teratoma 6%, and mixed NSGCT 79%; stage – I 46%, II 32%, and III 21%. Ten (7%) patients died from their NSGCT. Seven (5%) patients had incurable NSGCT. Multivariate analysis showed that presence of seminoma (p=0.007), presence of yolk sac tumor (p=0.019), clinical stage (p=0.027), and psychosocial issues (p=0.04), have unfavorable prognostic significance. Conclusions: Certain subtypes of NSGCT containing yolk sac tumor and seminoma are inherently chemotherapy resistant and potentially lethal. Psychosocial factors can delay the diagnosis and treatment of patients with such tumors and adversely affect their clinical outcome. Results of this study need to be validated in another data base or a prospective clinical trial.