The value of the “map sign” in shear wave elastography for differentiating seminomas from non-seminomas

Diagnosing testicular tumors that are negative for tumor markers using ultrasound and MRI is currently challenging. Seminomas and non-seminomas of the testis have different clinical diagnoses and treatment plans. Shear wave elastography (SWE) can reflect tissue stiffness, aiding in tumor type differentiation. This study aims to explore the diagnostic value of SWE color images in differentiating seminomas from non-seminomas of the testis by analyzing their characteristic features. A retrospective analysis was conducted on the SWE features of 39 pathologically confirmed testicular tumors negative for tumor markers. Based on pathological results, the tumors were divided into seminoma and non-seminoma groups. Differences in conventional ultrasound and SWE features between the two groups were analyzed. There were no statistically significant differences in location, shape, echo type, echo uniformity, SWE maximum value and SWE average value between the seminoma and non-seminoma groups (all p > 0.05), with respective p-values of 0.256, 0.458, 0.847, 0.298, 0.394, and 0.245. However, 76% (16/21) of seminomas showed a “map sign” (predominantly blue with red streaks) on SWE, while 0% (0/18) of non-seminomas showed this sign. There was a statistically significant difference in SWE color image features between the seminoma and non-seminoma groups (p = 0.000). Using the “map sign” as a diagnostic criterion for seminomas, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 76.2%, 100%, 100%, 78.2% and 87.2%, respectively, showing a statistically significant difference compared to conventional ultrasound (p = 0.030). The “map sign” on SWE can accurately diagnose testicular seminomas, improving the accuracy of conventional ultrasound diagnosis. This technique is non-invasive, simple, and repeatable, and it holds promise as a new method for diagnosing testicular seminomas.