Synovial Sarcoma with Massive Myxoid Feature: A Case Report

ABSTRACT

Focal myxoid change in synovial sarcoma is not uncommon, although the presence of predominantly myxoid stroma is very rare. Recognition of synovial sarcomas with massive myxoid feature is important because these can easily be mistaken for other myxoid soft tissue neoplasms. We report a case of a synovial sarcoma with massive myxoid feature in the left thigh of a 54-year-old woman. Wide excision of an 8.5*7.0*5.0 cm, well-circumscribed and lobulated tumor was performed. The cut surface was gray, soft, and myxoid. Histological examination showed proliferation of spindle cells in the predominantly myxoid stroma. There were small areas with features more typical of synovial sarcoma, including uniform, spindled cells with fascicular growth patterns, collagenous stroma, mast cell infiltration, and hemangiopericytoma-like vascular patterns. Immunohistochemical examination showed focal positivity of the tumor cells for epithelial membrane antigen (EMA). Tumor cells were all negative for cytokeratin (AE1/AE3), cytokeratin 7, S-100 protein, smooth muscle actin, and desmin. Ultrastructurally, tumor cells showed desmosomes and microvilli. Our case underscores that, in order to make a correct diagnosis, immunohistochemical and ultrastructural examination is essential.