CASE HISTORY

This newborn baby boy from Paraguay presented with a large right hand soft tissue mass noticed since birth. A plain radiograph showed a large mass involving the soft tissues of the right hand, with extensive distortion of its normal anatomy.

 A biopsy was performed. The tumor was noticed to be composed of small round blue cells, suspicious for Ewing sarcoma vs other undifferentiated round cell sarcomas, including sarcomas with BCOR genetic alterations. Following this initial assessment, a right hand amputation with right axillary lymph node excision were performed. The case was sent in consultation to Dr. Zambrano for further classification, courtesy of Dr. Ingrid Rodríguez (Chief of Pathology at Hospital de Clínicas de la Facultad de Ciencias Médicas, Asunción, Paraguay).

Low power view shows a large soft tissue mass in close proximity to a distal phalangeal (finger) bone. 

The tumor is composed of relatively monotonous, morphologically undifferentiated small round blue cells with frequent delicate curvilinear vessels in the background.

Areas containing abundant myxoid (mucoid) stroma were also present.

In addition, the right axillary lymph node was positive for metastatic disease.

In view of these histologic findings, a sarcoma with BCOR genetic alterations was strongly favored, which was further supported by the diffuse nuclear expression of BCOR, cyclin D1 and SATB2 proteins.

Based on these histomorphologic and immunohistochemical results, the tumor was classified as a BCOR-rearranged sarcoma, consistent with primitive myxoid mesenchymal tumor of infancy (PMMTI) a neoplasm characterized by the presence of internal tandem duplications (ITDs) of the BCOR gene.