Malignant mesenchymoma is an interesting but very rare tumor in which malignant differentiation has occurred twice or more. We report a case of retroperitoneal malignant mesenchymoma consisting of osteosarcoma, leiomyosarcoma, liposarcoma and fibrosarcoma. Abdominal CT showed a large retroperitoneal mass with two separate and distinct parts, namely an area of prominent calcification and one of clearly enhancing solid components. The mass contained histologically distinct tumorous components with no histologic admixure at the interfaces. The densely calcified nodule corresponded to osteosarcoma, and the noncalcified clearly enhancing nodules to leiomyosarcoma, liposarcoma and fibrosarcoma.
Case Report ; Fibrosarcoma/*radiography ; Human ; Leiomyosarcoma/*radiography ; Liposarcoma/*radiography ; Male ; Mesenchymoma/*radiography ; Middle Age ; Osteosarcoma/*radiography ; Retroperitoneal Neoplasms/*radiography ; Tomography, X-Ray Computed

Tumor-induced osteomalacia (TIO), or oncogenic osteomalacia (OOM), is a rare acquired paraneoplastic disease characterized by renal phosphate wasting and hypophosphatemia. Recent evidence shows that tumor-overexpressed fibroblast growth factor 23 (FGF23) is responsible for the hypophosphatemia and osteomalacia. The tumors associated with TIO are usually phosphaturic mesenchymal tumor mixed connective tissue variants (PMTMCT). Surgical removal of the responsible tumors is clinically essential for the treatment of TIO. However, identifying the responsible tumors is often difficult. Here, we report a case of a TIO patient with elevated serum FGF23 levels suffering from bone pain and hypophosphatemia for more than three years. A tumor was finally located in first metacarpal bone by octreotide scintigraphy and she was cured by surgery. After complete excision of the tumor, serum FGF23 levels rapidly decreased, dropping to 54.7% of the preoperative level one hour after surgery and eventually to a little below normal. The patient's serum phosphate level rapidly improved and returned to normal level in four days. Accordingly, her clinical symptoms were greatly improved within one month after surgery. There was no sign of tumor recurrence during an 18-month period of follow-up. According to pathology, the tumor was originally diagnosed as "lomangioma" based upon a biopsy sample, "proliferative giant cell tumor of tendon sheath" based upon sections of tumor, and finally diagnosed as PMTMCT by consultation one year after surgery. In conclusion, although an extremely rare disease, clinicians and pathologists should be aware of the existence of TIO and PMTMCT, respectively.
Bone Neoplasms ; blood ; complications ; diagnostic imaging ; pathology ; surgery ; Female ; Fibroblast Growth Factors ; blood ; Follow-Up Studies ; Humans ; Hypophosphatemia ; blood ; diagnostic imaging ; etiology ; pathology ; surgery ; Mesenchymoma ; blood ; complications ; diagnostic imaging ; pathology ; surgery ; Metacarpal Bones ; Middle Aged ; Neoplasms, Connective Tissue ; blood ; complications ; diagnostic imaging ; pathology ; surgery ; Osteomalacia ; blood ; diagnostic imaging ; etiology ; pathology ; surgery ; Phosphates ; blood ; Radiography