Primary malignant mixed tumor of bone: a case report

Abstract

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.

Keywords: Primary malignant mixed tumor; bone.

Figure 1

X-ray plain revealed a translucent expansive lesion with thinning, absorption and, partial discontinuity of cortical bone in the left greater trochanter.

Figure 2

A. The tumor cells were spindle, arranged in cords and strands forming a vague lobular pattern, embedded in a myxoid stroma. B. Epithelioid tumor cells that had round to oval, vesicular nuclei, inconspicuous nucleoli, and eosinophilic cytoplasm, with mild nuclear pleomorphism and an increased mitotic activity (Red arrows) (H&E stain). C. The cords of epithelioid cells with clear cytoplasm were scattered in a myxoid or myxochondroid stroma and transited into squamous epithelial cells with keratin pearl formation (H&E stain). D. Small foci of cellular cartilage with nuclear atypia, consistent with low grade chondrosarcoma were found scattered throughout the tumor (H&E stain). E. The dense spindle tumor cells with coagulative necrosis infiltrated between bone trabeculae (H&E stain). F. The tumor cells were positive for p63 strongly and diffusely with a pattern of nuclear staining. G. The spindle tumor cells were strongly positive for S-100 protein.