[94] Primary Malignant Myoepithelial Tumor of Bone

Yaxia Zhang, G Petur Nielsen, Kevin Raskin, Nicole Cipriani, Andrew E Rosenberg. University of Miami, Miller School of Medicine-Jackson Memorial Hospital, Miami, FL; Massachusetts General Hospital, Boston, MA

Background: Primary malignant myoepithelial tumor of bone is a rare malignancy which can resemble morphologically a variety of different tumors including chordoma, myxoid chondrosarcoma, and carcinoma. To increase our understanding of the clinicopathologic features of this unusual neoplasm we reviewed our experience with 6 cases.
Design: The study cohort was identified from the authors consult files and from the surgical pathology files of Massachusetts General Hospital and University of Miami Hospital. The clinical and pathological features of the tumors including their histologic, immunohistochemical, and EWSR1 status were analyzed.
Results: The patients included 3 females and 3 males who ranged in age from 18-57 (mean of 41.3) years. The tumor location included: 1 in the maxilla, 1 in the distal tibia, 1 in the calcaneus, 2 in the mandible, and 1 in the distal femur. Imaging studies showed that the tumors were lytic with cortical destruction and extra-osseous extension. Microscopically, four cases were composed of clusters of large epithelioid and spindle cells enmeshed in a prominent basophilic myxoid stroma. The other two cases were hypercellular and composed of clusters of epithelioid cells and spindle cells with solid and reticular pattern. The tumor cells demonstrated pleomorphism, and high mitotic activity and variable amounts of necrosis. The tumors also infiltrated into the surrounding soft tissue. Immunohistochemically, the tumor cells were focally positive for either S100/ or SMA and EMA/or Keratin. Four cases were analyzed by FISH for detection of EWSR1 gene rearrangement and one case had a rearrangement, one tumor demonstrated monosomy of chromosome 22, one case was inconclusive, and one case was negative. All patients underwent wide resection.
Conclusions: Primary malignant myoepithelial tumor is a rare bone tumor, is heterogenous morphologically, and can be confused with a variety of different neoplasms. Immunohistochemically these tumors usually express S100 and EMA and have genetic aberrations involving chromosome 22. As very few of these tumors have been described their optimal treatment and natural history needs to be better defined.
Category: Bone & Soft Tissue

Tuesday, March 5, 2013 1:00 PM

Poster Session IV # 14, Tuesday Afternoon


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