Testicular germ cell tumors (TGCTs) include various malignancies with distinct pathologies that share a common precursor lesion (intratubular germ cell neoplasia, unclassified, ITGCNU, or carcinoma in situ, CIS). TGCTs, as a whole, represent a highly curable tumor paradigm, with high sensitivity to radiotherapy and, especially, to cisplatin-based chemotherapy. However, a percentage of cases display therapeutic resistance, and the molecular mechanisms underlying such resistant phenotype remain to be elucidated. We put forward the notion that expression of oncogenic forms of the PCPH gene, which are known to confer resistance to radiation and chemotherapeutic drugs, including cisplatin, may be expressed in TGCTs, and thus contribute to the development of therapeutic resistance. To begin testing this concept, we studied PCPH expression in human TGCT cell lines and in 54 solid tumors by RT-PCR, western immunoblot and immunohistochemistry. The results demonstrated that: i) PCPH is expressed in TGCT cell lines and tumors, including CIS; ii) its expression levels vary among different TGCT pathologies, being generally higher in well differentiated regions and lower in areas of predominant proliferation; iii) PCPH expression is substantially increased in tumors relative to matched normal testicular tissue; iv) tumor samples express PCPH polypeptides of low molecular mass, consistent with the known size of the PCPH oncoprotein, that are either absent from, or markedly reduced in, matched normal tissue. Collectively, these results positively identify PCPH as a good early molecular marker for testicular neoplasms, and strongly indicate that immunodetection of truncated PCPH polypeptides may be a useful diagnostic tool for TGCT.