The large variegated mass in this nephrectomy specimen and MRI scan is a renal cell carcinoma, the most common primary malignancy of the kidney in an adult. Persons who smoke are at increased risk for this type of cancer. In most cases, there are no early symptoms, so that the tumor may no longer confined to the kidney when it is found, having invaded the renal capsule or the renal vein. Hematuria is the most frequent sign, but a fourth of cases initially present with a metastatic lesion. The metastases can be in unusual places. Ordinarily, the presence of metastases connotes a poor prognosis, but some patients with renal cell carcinoma do well following removal of localized metastatic lesions, in addition to nephrectomy. Paraneoplastic syndromes often accompany renal cell carcinoma and can include polycythemia, hypercalcemia, and Cushing syndrome, among others.