A Novel IRF2BP2::CDX2 Gene Fusion in Digital Intravascular Myoepithelioma of Soft Tissue: An Enigma!

Soft tissue myoepitheliomas (STM) are benign myoepithelial neoplasms (of non-salivary gland origin) arising, most commonly within subcutaneous and deep soft tissues of the extremities and rarely within bones. To the best of our knowledge, the intravascular location of STM as well as the identification of a novel IRF2BP2::CDX2 fusion have not been previously reported. Herein, we report a case of spindle cell myoepithelioma arising within the intravascular space of the right index finger in a 52-year-old male of more than 20-years duration. Histopathology demonstrated an intravascular tumefactive lesion composed of predominantly plump banal spindle cells in a fascicular arrangement within a mixed collagenous and chondromyxoid stroma colliding with papillary endothelial hyperplasia (Masson tumor). By immunohistochemistry, the lesional cells were positive for keratin-AE1/3, EMA, S100, SOX10, GFAP, calponin and negative for CD34, SMA, desmin, p63, and ERG. Fluorescence in situ hybridization for EWSR1 gene rearrangement was negative. Next generation sequencing detected a novel IRF2BP2::CDX2 fusion involving exon 1 of the IRF2BP2 gene and exon 2 of the CDX2 gene and confirmed by RT-PCR and Sanger sequencing. Further, clinical evaluation for a salivary gland mass elsewhere in the head and neck region and MRI of the chest, abdomen and pelvis were performed with no evidence of tumor elsewhere. Taken together, overall features were considered diagnostic of STM. Our current case underscores the novelty of the IRF2BP2::CDX2 gene fusion in STM and its exceptionally rare intravascular location. This article is protected by copyright. All rights reserved.