Thymidylate synthase 1 (TS1) in-situ protein expression predicts the survival of Ewing/PNET

Thymidylate synthase (TS1), RRM1, and ERCC1, which are crucial for DNA synthesis and repair and have shown prognostic and predictive value in carcinomas, were investigated in Ewing/primitive neuroectodermal tumor (PNET). The tissue microarray consisting of 31 archived Ewing/PNET samples was subjected to immunohistochemistry based on immunofluorescence combined with automated quantitative analysis (AQUA) to assess in-situ expression. Automated quantitative analysis score was analyzed with various clinicopathologic data. TS1 was immunoreactive in the nucleus and cytoplasm, while RRM1 and ERCC1 were nuclear. High TS1 expression, not RRM1 and ERCC1, was associated with long overall survival (p value = 0.057). Thus in-situ TS1 protein expression in Ewing/PNET is a prognostic marker.