Spontaneous regression of metastatic clear cell renal cell carcinoma: A report of a rare case and a review of the literature.

Renal cell carcinoma (RCC) is the seventh most common cancer in the United States; clear cell RCC (ccRCC) is the most common subtype. We report a case of spontaneous regression of metastatic ccRCC and discuss possible underlying mechanisms informed by a literature review. While regression of metastatic RCC has been described following nephrectomy or treatment of the primary tumor, spontaneous regression is rare. Postulated underlying causes include tumor necrosis and immune-mediated responses. Of 29 identified cases of spontaneous regression, only ours occurred after only a biopsy. Better understanding of the pathophysiology of spontaneous regression in RCC will improve its management.