Ultrasonography-guided trucut biopsy of retroperitoneal mass is performed and the pathological anatomy is sent. It is reported as a neoformation consisting of small non-smooth cells germ cells that are arranged in nests, with small non-smooth cells, small nuclei and small lymphocytic cells with small nuclei; there are small nuclei; there are non-smooth positive nuclei; there are small nuclei; there are small nuclei; there are non-smooth