DAZ-like 1( DAZL1) is a germ cell-specific protein expressed in both male and female gonads. The DAZL1 gene, which maps to chromosome 3 in humans, is an autosomal homologue to the Deleted in AZoospermia ( DAZ) gene(s) located on the Y chromosome. We studied the expression of DAZL1 by means of immunohistochemistry in order to determine its distribution among testicular germ cell neoplasias and among the intratubular lesions in their vicinity. Our results demonstrated that expression of DAZL1 protein was consistently observed in scattered cells in all intratubular germ cell neoplasias (IGCN) of the unclassified type, as well as in some of the intratubular seminomas. Foci of DAZL1 immunopositive cells were detected in pure seminomas, while single immunopositive cells were dispersed in the seminomatous component of mixed germ cell neoplasias. All the nonseminomatous components were negative for DAZL1 expression. These findings demonstrate an antigenic heterogeneity of seminoma cells. The localization of a specific germ cell protein, DAZL1, in the putative ontogenic progenitor, IGCN, and in their putative derivative, seminoma, provides further support for the hypothesis that IGCN is the precursor of germ cell neoplasias.