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A Subset of Ectomesenchymal Chondromyxoid Tumors of the Tongue shows EWSR1 Rearrangements and is Genetically Linked to Soft Tissue Myoepithelial Neoplasms: A study of 11 cases

2016-03-24 13:07:48

Histopathology; 24 March 2016: DOI: 10.1111/his.12973

Prokopios P. Argyris, Elizabeth A. Bilodeau, Aaron E. Yancoskie, Denise Trochesset, Stefan E. Pambuccian, Stephanie L. Wetzel, Sonal S. Shah, Morris Edelman, Paul Freedman, Michelle Dolan and Ioannis G. Koutlas



Abstract


Aims


Ectomesenchymal chondromyxoid tumor (ECT) is a rare, benign intraoral neoplasm showing predilection for the anterior dorsum of the tongue. The World Health Organization (W.H.O.) includes ECT in the pathologic spectrum of soft tissue myoepithelioma. EWSR1 rearrangement is identified in 45% of cutaneous, soft tissue and bone myoepithelial neoplasms, while PLAG1 aberrations are found in 37% of EWSR1-negative soft tissue myoepitheliomas. The aim of this study was to evaluate the presence of EWSR1 and PLAG1 rearrangements in ECTs.



Method and Results


Eleven formalin-fixed, paraffin-embedded ECTs were evaluated using FISH probes to EWSR1 (22q12) and PLAG1 (8q12). Among the 11 ECT cases tested, 3 (27.3%) showed EWSR1 rearrangement in >15% of tumor cells, while 8 (72.7%) cases did not show EWSR1 rearrangement. Eight of 9 (89%) ECTs demonstrated gain of EWSR1, likely representing gain of all or part of chromosome 22, in a varying proportion of neoplastic cells ranging between 1.4-27.9%. PLAG1 rearrangement was not detected in the successfully hybridized tissue sections (7/11). No correlation was observed between the molecular and histopathologic findings such as morphology of the neoplastic cells, presence of atypia, and matrical type.

Conclusions


We identified EWSR1 rearrangement in > 25% of ECTs. These results suggest that some ECTs are at least genetically related to myoepithelioma of the soft parts. Finally, PLAG1 aberrations do not appear to be critical in the pathogenesis of ECT of the tongue.

Key Words


EWSR1 rearrangement | PLAG1 rearrangement | ectomesenchymal chondromyxoid tumor | soft tissue myoepithelioma | myoepithelial neoplasm