Differentiation of testicular seminoma and nonseminomatous germ cell tumor on magnetic resonance imaging

Magnetic resonance imaging (MRI) has excellent soft tissue resolution, as well as multidirectional and multisequence scanning technology, making it an important supplementary method in the diagnosis of testicular tumor. To explore the utility of preoperative MRI for the differential diagnosis of testicular seminoma and nonseminomatous germ cell tumors (NSGCTs). The medical records from 39 patients with testicular tumors that were examined preoperatively with MRI and treated with urologic surgery at our institution between January 2015 and March 2019 were retrospectively reviewed. Testicular tumors were confirmed by pathology and classified as seminoma (n=20) or NSGCT (n=19). Two radiologists analyzed the testicular tumors on preoperative MRI for morphology: multiple nodules or a single mass; presence/absence of a capsule; signal compared to the normal contralateral testicle (isointense, hypointense, hyperintense, or mixed); enhancement; septa; and hemorrhagic or cystic degeneration. Characteristics of seminomas and NSGCT were compared using the Chi-square or Fischer exact test. MRI showed that the majority (95%; 19/20) of seminomas were nodular. There were significant differences in the presence/absence of a capsule (P=.001), T1-weighted imaging (T1WI) signal intensity (P=.047), T2-weighted imaging (T2WI) signal intensity (P<.001), septa (P<.001), and hemorrhagic or cystic degeneration (P<.001) between seminomas and NSGCT. Seminomas were more likely to have no capsule, isointensity on T1WI, hypointensity on T2WI, and had narrow obviously enhanced fibrovascular septa without hemorrhagic or cystic degeneration; NSGCT was more likely to have a capsule, a mainly mixed signal on T1WI and T2WI, most of them had no fibrovascular septa, and hemorrhagic or cystic degeneration was common in malignant NSGCT. This study suggests that preoperative MRI can distinguish seminoma from NSGCT. We propose that preoperative MRI of the scrotum is an effective technique that should be widely adopted for the management of scrotal disease.