Undiff. Pleomorphic Sarcoma : Introduction

Comments:
Introduction: Undifferentiated pleomorphic sarcoma (UPS) is a high-grade sarcoma arising in deep soft tissues in elderly patients. It was previously known as malignant fibrous histiocytoma (MFH) and included a wide range of high-grade pleomorphic sarcomas with varied histogenesis.

With the increased use of ancillary studies such as newer immunohistochemical markers and molecular techniques, many cases that would have been previously labeled as MFH are now appropriately classified as lineage-specific sarcomas, including pleomorphic variants of leiomyosarcoma, rhabdomyosarcoma or liposarcoma. De-differentiated retroperitoneal liposarcomas resemble UPS. In addition, sarcomatoid carcinomas, sarcomatoid mesothelioma, melanoma, or even anaplastic lymphoma can have pleomorphic appearance and mimic UPS.

UPS has a broad spectrum of morphologic appearances and it can be divided into four subtypes: storiform-pleomorphic (prototypic UPS, 70% of cases; shown here), myxoid (myxofibrosarcoma, 20% of cases), inflammatory, and giant cell type. Most cases show an admixture of pleomorphic and storiform areas with sheets of polygonal, spindled and epithelioid cells, abundant eosinophilic cytoplasm, marked nuclear pleomorphism, multinucleation, necrosis and conspicuous mitotic activity, including atypical forms.