Testicular cancer elastographic characterization (seminomas and nonseminomatous germ cell tumors, technical aspects)
Ultrasound elastography was done to 31 patients (19-65 years old) with malignant testicular tumors. In all cases lesions were unilateral, and diagnosis was confirmed morphologically (seminoma - 18 (58.1%), embryonal carcinoma - 5 (16.1%), mixed germ cell tumors - 7 (22.6%), spermatocytic seminomas - 1 (3.2%)). All patients were divided into groups depending on the morphological type of tumors: 1) seminoma (n = 18) and nonseminomatous germ cell tumors (n = 12); 2) teratoma as a component of mixed germ cell tumor (n = 6) and other germ cell tumors (n = 25). Shear wave elastography was used after testes gray scale visualization (Aplio 500 (Toshiba, Japan) and Aixplorer (Supersonic Imagine, France) with linear probes 4-15 and 5-14 MHz respectively). Technical aspects: the difference between Young’s modulus values measured in testicular tumors by using Aplio 500 (1) and Aixplorer (2) were nonsignificant (P = 0.95). Correlation between Young’s modulus measured on two ultrasound systems was high (R<sub>s</sub> = 0.86, P = 0.0137). The values of Young’s modulus in testicular tumors were significantly higher in compare to echographically intact ipsilateral testicular parenchyma (P = 0.0017 for these comparisons on two ultrasound systems) and contralateral testicular parenchyma (P = 0.0017 for these comparisons on two ultrasound systems). There was no significant difference between Young’s modulus values in two testes (echographically intact ipsilateral testicular parenchyma and middle segment of contralateral testis) (P = 0.4057 and P = 0.8480 for ultrasound systems 1 and 2, respectively). Morphological aspects (Aixplorer ultrasound system): Emean median in the group of seminoma (n = 18) was 110.3 kPa, 25-75<sup>th</sup> percentiles - 77.6-159.0 kPa, 5-95<sup>th</sup> percentiles - 16.5-222.1 kPa, minimum - maximum values - 15.3-241.4 kPa; in the group of nonseminomatous germ cell tumors (n = 12) - 109.9 kPa, 83.0-129.0 kPa, 55.5-156.8 kPa, 54.2-157.8 kPa (P = 0,9325). Nonsignificant difference was also identified when comparing mixed germ cell tumors with teratoma and other tumors (P = 0.5823). Significant difference in values of stiffness (elasticity) indexes (stiffness ratio 1 - ratio of Emean values in the stiffest tumor areas and echographically intact ipsilateral testicular parenchyma, stiffness ratio 2 - ratio of Emean values in the stiffest tumor areas and contralateral testicular parenchyma, stiffness ratio 3 (intratumoral stiffness ratio) - ratio between the maximum and minimum stiffness inside the tumor) in patients with seminoma and nonseminomatous germ cell tumors was also not found.