Soft tissue myoepithelial carcinoma without EWSR1 gene rearrangement and poor outcome. A case report

Soft tissue myoepithelial carcinomas (STMM) are clinically aggressive tumors that arise in the extremities and limb girdles of young patients. Histologically, they show moderate to severe atypia and infiltrative margins. EWSR1-gene rearrangements are present in 45% of cases and are associated with increased malignancy.A large mass in the right hip of a 26-year-old male that had been surgically removed showed strands of cells embedded in a hyalin-myxoid matrix without ductal differentiation. Cells expressed cytokeratins, EMA, S-100 protein and calponin. STMM was diagnosed. Although the tumor did not have an EWSR1 gene rearrangement, it behaved aggressively and the patient died from multiple metastases 18 months after diagnosis.

ResumenLos carcinomas mioepiteliales de partes blandas (STMM), afectan a las extremidades o cinturas de pacientes jóvenes y evolucionan agresivamente. Muestran una marcada atipia y bordes infiltrantes y su pronóstico empeora con el reordenamiento del gen EWSR1, presente en el 45% de los casos.Presentamos el caso de un varón de 26 años al que se le extirpó un STMM situado en la cadera derecha, compuesto por cordones y nidos sólidos de células atípicas rodeadas de un estroma mixoide-hialino, sin diferenciación ductal. Expresaban citoqueratinas, EMA, S100 y calponina. La hibridación in situ fluorescente (FISH) no reveló reordenamientos del gen EWSR1. Tras recibir cuidados paliativos, el paciente murió por múltiples metástasis a los 18 meses del diagnóstico. Se trata de un caso de STMM sin reordenamiento del gen EWRS1 pero inusualmente agresivo.