[57] Primary Myoepithelioma of Bone.

Pawel J Kurzawa, Petur G Nielsen, Susan Kattapuram, Francis J Hornicek, Andrew E Rosenberg. Great Poland Cancer Centre, Poznan, Wielkopolska, Poland; Massachusetts General Hospital, Boston

Background: Myoepithelial tumors are diverse in their morphology and biology. They are composed of neoplastic cells that may be purely myoepithelial in phenotype (myoepithelioma) and in some cases these tumors may also contain a second population of cells that are epithelial in differentiation. Recently, this tumor has been shown to harbor a rearrangement of the EWSR1 gene on chromosome 22 in 45% of cases. Myoepithelioma has been described to arise in salivary glands, skin, upper airway, lung, gastrointestinal tract, breast, soft tissue, and rarely in bone. To increase our understanding of intra-osseous myoepithelioma we reviewed our experience with 8 cases.
Design: The study cohort was identified from the authors consult files and from the surgical pathology files of MGH. The clinicopathologic characteristics of the tumors including their histologic and immunohistochemical features, and status of translocation involving the EWSR1 gene were analyzed.
Results: The patients included 5 females and 3 males who ranged in age from 16-49 (mean of 33.5) years. The tumor locations included: 3 in the ilium, 2 in the tibia, and 1 each in the maxilla, sacrum, and L1. Radiographically 6 of the lesions were limited to the bone and were lytic or mixed sclerotic and lytic in appearance. Two tumors breached the cortex and extended into the soft tissues and grew with pushing margins. Histologically the tumors were composed predominantly of spindle cells with variable numbers of epithelioid cells some of which had clear or eosinophilic cytoplasm. The stroma was hyalinized, collagenous or myxoid. Immunohistochemically, all tumors were positive for S-100 and 7 were positive for EMA (1 negative case had a EWSR1 gene rearrangement). None of the tumors were positive for keratin cocktail. FISH for EWSR1 rearrangement was performed in 7 tumors; 5 tumors (71%) were positive and 2 tumors (29%) were negative. Treatment in 5 patients consisted of curettage, 1 is scheduled to be resected in the near future and the data of two patients is not currently available. Follow-up available on 3 patients ranges from 4-35 months (mean 18 months) and all have remained free of disease with no local or disseminated recurrence.
Conclusions: Primary myoepithelioma is a rare primary bone tumor and can be confused with a variety of different neoplasms. Immunohistochemically, they usually express S100 and EMA and have a gene rearrangement involving EWSR1. In our series the tumors had benign histological features, and although follow-up is limited, they have not behaved in an aggressive fashion.
Category: Bone & Soft Tissue

Monday, February 28, 2011 9:00 AM

Platform Session: Section F, Monday Morning


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