An association between renal cell carcinoma and multiple myeloma: a case series and clinical implications.

Objective: To describe an association between renal cell carcinoma (RCC) and multiple myeloma (MM) in patients with both disorders, and suggest possible explanations for the association.

Patients And Methods: We retrospectively reviewed the records of patients with MM and RCC at the Cleveland Clinic between 1990 and 2005, and identified 1100 with MM, 2704 with RCC and eight with concomitant MM and RCC. The medical records of these eight patients were reviewed.

Results: In four of the eight patients, RCC was diagnosed after the MM at 3, 8, 23 and 46 months, respectively; in the remaining four, the RCC was diagnosed before MM by 108, 35, 13 and 1 months, respectively. The number of cases of RCC expected in the present 1100 patients with MM over 15 years was lower than the four recorded (P < 0.001, Fisher's exact test). Similarly, the number of cases of MM expected in the 2704 patients with RCC was also lower than the four recorded (P < 0.001, Fisher's exact test).

Conclusions: RCC and MM can occur in the same patient at an incidence higher than the expected rate. Possible explanations include genetic abnormalities, environmental exposures or immune-related mechanisms predisposing to the second malignancy. These findings are particularly relevant in the management of patients with known RCC and lytic bone lesions, or those with known MM and subsequent or concomitant renal masses, especially those involving the right kidney.