Primary malignant mixed tumor of bone: a case report.

BACKGROUND: An extremely rare primary mixed tumor occurring in left proximal femurs of a 47-year old female is reported. CASE REPORT: She had left hip pain for three months in April 2004. Radiological examinations revealed that a translucent expansive lesion in the left greater trochanter. She received the curettage of lesion and bone graft surgery. Curettage specimens were diagnosed as malignant mixed tumor, considered to be metastatic. Five months late the lesion recurred. She underwent obturator neurotomy plus total hip replacement of left hip. A long-term of more than ten years follow-up showed there were no evidence of disease recurrence or metastasis and no any signs of other tumor in her body. DISCUSSION: The tumor contained myoepithelial component with positive immunostain of S-100 protein, p63, CK-pan, and vimentin, epithelial component confirmed by CK-pan, CK-LMW and cartilage, which indicated the tumor was a mixed tumor. Cellular atypia, relative high mitosis index, cartilage consistent with grade I chordrosarcoma, focal coagulative necrosis, and infiltration between trabeculae found in the tumor indicated that the tumor had a low grade malignant nature. During long-time follow-up there were no signs of any tumor found in the patient, which strongly suggested that the tumor be a primary one.