From an epidemiological point of view, testicular germ cell tumors are rare tumors, and represent 1 to 2% of cancers in men [7] (3.5% of tumors of the urogenital system). They are the leading cause of solid tumors in young men with a peak incidence between 30 and 34 years of age [14].

The post pubertal yolk sac tumor, also called endodermal sinus tumor, is a malignant germ cell tumor whose morphological aspects are reminiscent of extra embryonic structures: yolk sac, allantois and extra embryonic mesenchyme. Most patients are between 15 and 40 years of age, although later cases have been described [15]. The yolk sac tumor is almost always part of a mixed germ cell tumor and is found in 44% of TGNS.Pure forms are exceptional representing 0.6% of germ cell tumors of the testis [7]. In this case, the yolk sac tumor was a pure form, occurring in a 25-year-old patient with right testicular ectopia; it was a tumor differentiated in the extraembryonic sense. Some risk factors for germ cell tumors are consensual [8] testicular dysgenesis syndrome (cryptorchidism, hypospadias, hypo or infertility), personal or family history of TG, testicular atrophy (<12ml), others are discussed such as heavy cannabis use, pesticides, organic solvents, morphometry [9].

Testicular Doppler ultrasonography is the examination indicated as the first line of treatment for intragonadal germ cell tumors. It has a sensitivity close to 100% for the positive extra and intra-testicular diagnosis of a scrotal mass [4].It allows confirmation of the presence of a tissue process by specifying the site, the semiological characteristics: size, contours, limits, echogenicity (it typically shows a hypoechoic intra-testicular image), and the vascular nature of the tumour, and thus it explores the contralateral testicle and allows its surveillance. The risk of developing a second tumor is increased if there are grade 3 micro-calcifications [11]. In our series, ultrasound revealed a well-limited oval abdominal and pelvic tumour process, with a tissue echostructure and a minority cystic component measuring 168x102x155m with bilateral pyelocalic dilatation.

The learned societies of radiology (SFR, HAS) consider that CT-PET is systematically recommended for the initial assessment and follow-up of TG without and with injection of iodinated contrast medium, and allows the detection of lesions larger than 3 mm, showing a mixed mass, solid or cystic with significant heterogeneity due to hemorrhage or necrosis, Calcifications are noted in 40% of the situations, as shown in our case where the TAP CT mentioned a voluminous heterodense abdomino pelvic process containing a zone of liquefaction and fleshy contents as well as vessels inside with uretero hydro nephrosis The sensitivity of 80% for the analysis of retroperitoneal adenopathies and the evaluation of their size according to the largest transverse diameter (RECIST criteria) [5] allows the initial staging of this lymph node extension from N1 to N3 (16) (Table 1).

Testicular cancers metastasize by lymphatic and hematogenous routes. The first lymphatic relays are the latero-aortic areas immediately under the kidneys: indeed, in the embryo, the testis forms near the kidneys and then descends into the bursa. At a more advanced stage, the supra-diaphragmatic, mainly left supra-clavicular, and mediastinal nodes may be invaded.

Hematogenous dissemination occurs via the spermatic vein and the inferior vena cava: it is mainly responsible for pulmonary localizations, as in our patient's case, and, much more rarely, for hepatic, cerebral and bone localizations. It should be noted that in 10% of cases, the histological nature of the metastases differs from the primary germ cell tumor. Finally, it should be noted that rare germ cell tumors are extragonadal, retroperitoneal, mediastinal or pineal in location including.

Table 1 : TNM classification for testicular cancer.