Osteomalacia, renal Fanconi syndrome, and bone tumor

We herein report two cases of Fanconi syndrome with refractory hypophosphatemic osteomalacia that was difficult to correct by phosphorus replacement therapy. The pathological result was a bony giant cell tumor and osteosarcoma, respectively. Interestingly, after resection of the tumors, the patient with osteosarcoma recovered completely but the patient with the bony giant cell tumor had a relapse. Although she underwent nine operations, her symptoms and laboratory tests did not improve. These findings indicate that Fanconi syndrome can result from a bone tumor.