[33] Extraskeletal Myxoid Chondrosarcoma Presenting as a Primary Bone Tumor: Four Cases with Molecular Confirmation

Elizabeth G Demicco, Wei-Lien Wang, Julia A Bridge, Dali Huang, John E Madewell, Jeanne M Meis. The University of Texas M. D. Anderson Cancer Center, Houston, TX; University of Nebraska Medical Center, Omaha, NE

Background: The existence of primary bone tumors identical to extraskeletal myxoid chondrosarcoma (EMC) of soft tissue has been controversial due to lack of adequate imaging, histological and molecular documentation. We present 4 cases of EMC in bone that prove it may occur as a primary bone tumor.
Design: Our institutional files were searched for cases of EMC with bone involvement. Imaging features were reviewed by an expert bone radiologist. Clinical and histological features were reviewed to establish the diagnosis, and FISH using break-apart probes for NR4A3 and EWSR1 was performed to confirm the diagnosis in all 4 cases.
Results: Four of 128 cases of EMC presented in bone (3%) and were confirmed on imaging studies to be primary bone tumors. Three presented as large intraosseous tumors with cortical breakthrough and soft tissue extension and one was primarily intraosseous (Table 1). Two cases were cellular EMC and 2 classical. NR4A3 gene rearrangement was found in 3 cases, with one being a variant NR4A3 rearrangement. EWSR1 rearrangement was found in 3 cases, including the NR4A3 negative case that could possibly represent an insertion.
All patients underwent wide resection and 2 adjuvant therapy. Two patients had metastases; one of these died of disease and the other underwent metastasectomy of pulmonary nodules and is currently disease free.
Conclusions: EMC of soft tissue may occur as a primary bone tumor. Failure to recognize this may lead to misdiagnosis. Molecular studies for NR4A3 and EWSR1 are important to establish the diagnosis. The biologic behavior and optimal treatment of this rare tumor are not clear at this time and require study of additional cases.

Table 1.
CaseAge (years) GenderSiteSize (cm)NR4A3 FISHEWSR1 FISHTreatmentOutcome
138 MIlium, sacrum, paraspinal muscles12++Pre-op CTRT, internal hemipelvectomyNED 5 mo
244 MMediastinum, manubrium6.7-+Wide resection, post-op RTLung mets, 26 mo
354 FIlium, gluteus muscles15++Pre-op RT, internal hemipelvectomyNED 36 mo
474 MAnterior 3rd rib2+-Wide resectionMultiple LR, 36 mo. Lung mets & DOD 61 mo
DOD - dead of disease, LR - local recurrences, mets - metastases, NED - no evidence of disease, RT & CT- radiation and chemo-therapy

Category: Bone & Soft Tissue

Tuesday, March 20, 2012 9:30 AM

Poster Session III # 1, Tuesday Morning


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