This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
Which one of the following variants of renal cell carcinoma has the worst prognosis - 
Select and explain. 
A. Papillary, B. Tubuloalveolar, C. Chromophobe, D. Sarcomatoid
D: Sarcomatoid
Answer: D: Sarcomatoid 
Explanation: None