Existing tumor markers for testicular germ cell tumor (TGCT) cannot detect the presence of pure teratoma. Serum miRNA have strong performance detecting other subtypes of TGCT. Previous reports suggest high levels of miR-375 expression in teratoma tissue. The purpose of this study was to explore the role of serum miRNA, including miR-375, in detecting the presence of teratoma at post-chemotherapy retroperitoneal lymph node dissection (PC-RPLND).

We prospectively collected pre-surgical serum from 40 TGCT patients undergoing PC-RPLND (21 with teratoma at RPLND, 19 with no evidence of disease). We examined the utility of serum miR-375-3p and -5p by qPCR, and searched for other putative serum miRNA with small RNA sequencing. Area under the receiver operating characteristic curve (AUC) and univariate analyses were utilized to evaluate test characteristics and predictors of teratoma.

Both serum miR-375-3p and -5p exhibited poor performance (-3p: 86% sensitivity, 32% specificity, AUC: 0.506; -5p: 55% sensitivity, 67% specificity, AUC: 0.556). Teratoma at orchiectomy was the only predictor of PC-RPLND teratoma. Small RNA sequencing identified 3 potentially discriminatory miRNA, but further validation demonstrated no utility. Our results confirm prior reports that serum miR-375 cannot predict teratoma, and suggest that there may not exist a predictive serum miRNA for teratoma.