Sclerosing Muc-4-positive sarcoma with glandular differentiation resembling sclerosing epithelioid fibrosarcoma

Sclerosing epithelioid fibrosarcoma is a rare soft tissue tumor that is composed of epithelioid fibroblasts embedded in an abundant extracellular collagenous matrix. They have been shown to be weakly epithelial membrane antigen (EMA) positive by immunohistochemistry and may contain intercellular junctions ultrastructurally. We present a case of a 52-year-old female who presented with a sclerosing Muc-4-positive sarcoma with glandular differentiation of the sciatic nerve, resembling sclerosing epithelioid fibrosarcoma. The glandular component showed strong expression of keratin and EMA and ultrastructurally showed numerous intercellular junctions and intraluminal microvilli, supportive of true glandular differentiation. The patient received preoperative radiotherapy (50 Gray) and subsequent resection of the mass with negative margins. She is currently disease free at 20-month follow-up. This case report describes an unusual sclerosing Muc-4-positive sarcoma with glandular differentiation, distinctive expression of epithelial immunohistochemical markers, and glandular differentiation by electron microscopy.