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Answer: (B) Mucinous tubular and spindle cell carcinoma.
Discussion: Clearly, this renal mass have tubular component (Panel A) and spindle cell component (Panel B) with mucin pools (Panel C and D). These feature are that of a mucinous tubular and spindle cell carcinoma of the kidney. The histology is distinctive enough to separate them from clear cell (conventional) renal cell carcinoma and oncocytoma. Metastatic sarcinoma and angiomyolipoma would lack the tubular component.