MicroRNA as a Liquid Biomarker to Detect Malignancy in Small Testicular Masses

Approximately 1-4% of individuals undergoing scrotal ultrasound are found with incidental small (≤2 cm) testicular masses (STMs), with the vast majority being benign (∼13-21% malignant). This study explores the potential of microRNAs (miRNAs) as liquid biomarkers for predicting germ cell tumors (GCTs) in STMs.

From 2009 to 2023, we identified patients with STMs who had banked serum/plasma prior to orchiectomy. Eligible samples were analyzed using different miRNA expression methods (reverse transcription quantitative polymerase chain reaction [RT-qPCR] and digital droplet polymerase chain reaction) and platforms across three research laboratory facilities (Portugal, Vancouver, and Toronto). The miRNA assays included 371a-3p, 372, 373, and 367. The primary objective was to evaluate the diagnostic accuracy of miR-371a-3p to predict the presence of testicular cancer using the area under the curve (AUC).

Our cohort included 61 patients: 37 patients with confirmed GCTs, 20 patients with benign histology, and four patients who had been on surveillance for >24 mo and were deemed to have benign STMs. Across all three laboratories, miR-371a-3p consistently outperformed all the miRNAs, with the other miRNAs proving uninformative. Extraction from plasma and an RT-qPCR analysis (Vancouver laboratory) proved best, with sensitivity of 87% and specificity of 91%, translating into an AUC of 0.93. The receiver operating characteristic scores for the other two laboratories were 0.77 and 0.73 for Portugal and Toronto, respectively. This single-center study is limited by a potential selection bias and fewer evaluable samples due to technical and logistical issues.

This is the largest series of STMs with banked blood/serum to date. Among the miRNAs, miR-371a-3p was found to be sensitive and specific for detecting the presence of GCTs in STMs. Plasma with an RT-qPCR approach proved to be a superior method of analysis.