1. ¹Department of Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
2. ²Department of Pathology, Texas Children's Hospital and Baylor College of Medicine, Houston, TX, USA
3. ³Department of Hematopathology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
4. ⁴Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
5. ⁵Department of Sarcoma Medical Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
6. ⁶Department of Cancer Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
7. ⁷Sarcoma Research Center, The University of Texas MD Anderson Cancer Center, Houston, TX, USA

Correspondence: Dr AJF Lazar, MD, PhD, Department of Pathology and Sarcoma Research Center, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Unit 0085, Houston, TX 77030, USA. E-mail: alazar@mdanderson.org

Received 10 March 2008; Revised 30 May 2008; Accepted 30 May 2008; Published online 27 June 2008.

Abstract

Extraskeletal myxoid chondrosarcoma is a rare soft tissue tumor characterized by a nodular growth pattern with eosinophilic cells usually in a reticular pattern and abundant myxoid stroma. In contrast to other myxoid sarcomas, the majority of extraskeletal myxoid chondrosarcomas harbor a balanced translocation, t(9;22)(q22;q12), that fuses EWSR1 with NR4A3 (also known as CHN). Other less common translocations involving NR4A3 have also been described. We examined the diagnostic utility of fluorescence in situ hybridization for extraskeletal myxoid chondrosarcoma using the LSI EWSR1 break-apart probe (Abbott Molecular/Vysis, Des Plaines, IL, USA). Sixteen cases of extraskeletal myxoid chondrosarcoma with formalin-fixed paraffin-embedded tissue available were retrieved (1991–2007). The mean age at time of presentation was 57 years (range, 30–78). The male to female ratio was 7:1. All cases where either consistent with or highly suggestive of the diagnosis, with most of the primary tumors occurring in the thigh, inguinal or gluteal region. Fifteen of 16 cases were analyzable, of which 14 (93%) were positive for the rearrangement of the EWSR1 locus. In this study, the vast majority of extraskeletal myxoid chondrosarcomas are associated with a rearrangement at the EWSR1 locus (22q12). Fluorescence in situ hybridization is useful to support the diagnosis of extraskeletal myxoid chondrosarcomas and may help to differentiate it from mimics such as other myxoid sarcomas, particularly in limited biopsies.