Dieckmann KP, et al. - Researchers intended to ascertain the utility of M371 test, that involves evaluation of serum levels of microRNA (miR)-371a-3p, as a novel biomarker for germ cell tumors (GCTs). Using quantitative polymerase chain reaction, serum levels of miRNA-371a-3p (miR levels) were determined in samples from 616 patients with testicular GCTs and 258 male controls. Overall 359 and 257 patients with seminoma and nonseminoma, respectively, were included in GCT population. Sensitivity and specificity of 90.1% and 94.0%, respectively, was yielded by the M371 test for the primary diagnosis of GCT. This test had a positive predictive value of 97.2% and in receiver operating characteristic analysis, an area under the curve of 0.966 was generated. With both a sensitivity and a specificity greater than 90%, the M371 test performed better than the classic markers of GCT. This marker was expressed by all histologic subgroups, except teratoma.