Cytology-histology correlation of myoepithelial tumors harboring EWSR1-POU5F1 fusions: A report of two cases.

Myoepithelial tumors (MET) constitute a group of neoplasms with a variety of morphologic, immunophenotypic, and molecular features. Approximately half of MET of soft tissue harbor EWSR1 gene rearrangements with a subset showing EWSR1-POU5F1 fusions and demonstrating distinctive tendency towards aggressive behavior in children. Histologically, EWSR1-POU5F1-positive MET typically show clear-cell morphology with malignant features including marked pleomorphism and atypical mitotic figures. The cytomorphology of these tumors has not been well characterized. Reported here are the cytomorphologic features of two cases of EWSR1-POUF1-positive MET with histology correlation.