Abstract Objectives To investigate the utility of a novel serum miRNA biomarker panel to distinguish teratoma from nonmalignant necrotic/fibrotic tissues or nonviable tumours in patients with NSGCT undergoing post‐chemotherapy consolidation surgery. Patients and methods We prospectively collected pre‐surgical serum samples from 22 consecutive testicular NSGCT patients with residual NSGCT after chemotherapy undergoing post‐chemotherapy consolidation surgery. We measured serum miRNA expression of four microRNAs (miRNA‐375, miRNA‐200a‐3p, miRNA‐200a‐5p and miRNA‐200b‐3p) and compared with pathologic findings at time of surgery. Receiver operating characteristic (ROC) curves were performed to assess the ability of these miRNA to differentiate between teratoma and necrosis or viable malignancy. Results Twenty‐two patients with NSGCT were split into two groups based on pathology at time of post‐chemotherapy consolidation surgery (teratoma group vs. necrosis/fibrosis/viable tumour group, i.e., NFVT). Patients with teratoma were older at diagnosis compared with those patients with NFVT (median age 28.7 vs. 23.9). Patients with NFVT were more likely to have embryonal carcinoma in their primary tumour (81.8% vs. 27.3%; p = 0.01). The majority of patients in both groups were stage III (63.6% vs. 72.7%). In this analysis, none of the miRNAs had good sensitivity or specificity to predict teratoma. There was no significant association between the expression levels of the miRNAs and the presence of teratoma. There was no statistically significant correlation between any of the miRNAs and teratoma size. Conclusion This novel miRNA panel (miRNA‐375, miRNA‐200a‐3p, miRNA‐200a‐5p and miRNA‐200b‐3p) did not distinguish teratoma from nonmalignant necrotic/fibrotic tissues or nonviable tumours in patients with NSGCT undergoing post‐chemotherapy consolidation surgery.
