RT Book, Section A1 Fritchie, Karen J. A1 John, Ivy A2 Reisner, Howard M. SR Print(0) ID 1173789351 T1 Soft Tissue and Bone Pathology T2 Pathology: A Modern Case Study, 2e YR 2020 FD 2020 PB McGraw-Hill Education PP New York, NY SN REISNERPATHOL LK accessmedicine.mhmedical.com/content.aspx?aid=1173789351 RD 2024/03/28 AB WHAT WE DOAlthough malignant neoplasms of soft tissue are relatively uncommon, accounting for about 0.6% of all cancer deaths in the United States in 2010, soft tissue pathology is often considered as an overwhelming and intimidating area. Soft tissue pathology includes a wide spectrum of tumors from several supportive nonepithelial tissue types mostly of mesodermal origin (adipose tissue, smooth muscle, skeletal muscle, etc.) and the peripheral nervous tissue of neuroectodermal origin. Additionally, there are a significant proportion of tumors that cannot be classified beyond the generic term “sarcoma” despite the use of immunohistochemical tools, cytogenetic techniques, and molecular studies. The simplest way to approach soft tissue pathology is to divide the tumors into groups based on the line of differentiation of the neoplastic population. Therefore, this chapter will systematically explore the different types of soft tissue neoplasms based on lineage. Within each subset of tumors (lipomatous, smooth muscle, nerve sheath, etc.), there is a certain set of rules or principles that provide an approach to diagnostic workup. An understanding of these rules helps the pathologist to navigate through each group of tumors. The overall approach to the analysis of soft tissue masses will start with imaging studies most often using CT or MRI technology to define the location and extent of tumor and assay for the presence of potential metastatic lesions. Early biopsy using fine-needle aspiration, core needle, or open incisional biopsy will provide tissue to allow classification, histological grading, and often cytogenetic or molecular analysis. The study of chromosomal abnormalities is of particular importance in the classification of certain soft tissue tumors. For example, about 95% of Ewing sarcomas (ES) (see later) have a translocation involving the EWS gene on 22q12.