A young male presents with abdominal pain. CT scan shows heterogenous necrotizing mass at left renal hilum. His AFP or hCG levels are elevated. The MOST likely diagnosis is:

Extragonadal germ cell tumors: Nonseminomatous extragonadal GCTs represent a distinct subset of GCTs and carry a poorer prognosis than primary testicular NSGCTs. The most common origin is the mediastinum, but they can also arise in the retroperitoneum or pineal region. Initial diagnosis may be aided by elevations of AFP or hCG. Ref: Brooks H.D., Pagliaro L.C., Lim Z.D., Pisters L.L., Tannir N.M. (2011). Chapter 36. Germ Cell Tumors. In H.M. Kantarjian, R.A. Wolff, C.A. Koller (Eds), The MD Anderson Manual of Medical Oncology, 2e.