Validation of tumor makers in central nervous system germ cell tumors by real-time reverse transcriptase polymerase chain reaction using formalin-fixed paraffin-embedded tissues

Abstract

The therapeutic protocols for treatment of germinomas and nongerminomatous germ cell tumors (NGGCTs) are completely different, so it is important to distinguish pure germinoma from NGGCTs. As it can be difficult to diagnose by morphology alone, immunohistochemistry (IHC) has been widely used as an ancillary test to improve diagnostic accuracy. However, IHC has limitations due to misinterpretation of results or aberrant loss of immunoreactivity. However, real-time RT-PCR has certain advantages over IHC, including its quantitative nature. The aim of our study was to evaluate the usefulness of real-time RT- 1PCR on formalin-fixed paraffin-embedded (FFPE) tissue blocks for the diagnosis of germ cell tumors of the central nervous system. We selected eight markers of germ cell tumors using a literature search, and validated them using real-time RT-PCR. Among them, POU5F1, NANOG, and TGFβ2 are statistically significant (p=0.05) in multiple comparisons (MANOVA) of three groups (pure germinoma, mature teratoma, and malignant germ cell tumor). Two-group (pure germinomas and NGGCTs) discriminant analysis achieved a 70.0% success rate in cross-validation. We concluded real-time RT-PCR using FFPE tissue has adequate validating power comparable to IHC in the diagnosis of central nervous system germ cell tumors; therefore, when IHC are not available, not conclusive, or not informative, RT-PCR is a potential alternative to a repeat biopsy.