There is a lot going on in this case. The major teaching point here is that the left pelvic sidewall adenopathy looks different from the retroperitoneal adenopathy suggesting that it is a different process. In this case, lymphoproliferative disorder was favored and US-guided biopsy was recommended for both the renal mass and left lower quadrant adenopathy separately. 

Final pathology showed that the RP lymph nodes were due to RCC mets, and the left lower quadrant nodal mass was unicentric Castleman disease.