Reversible migratory osteoporosis in renal oncocytoma mimicking renal cell carcinoma with bone metastases.

We report a case in which initially the wrong diagnosis of renal cell carcinoma with bone metastases was made. Nephrectomy and bone biopsy led to the right diagnosis of oncocytoma with transient osteoporosis. This report stresses the importance of pathological investigation and points to oncocytoma in the differential diagnosis of solid renal masses. In addition, the possible relationship between this tumour and migratory osteoporosis, which disappeared after surgery, is described.