A significant number of soft tissue tumors either show no clear line of differentiation or appear to differentiate along the lines of a cell type with no normal counterpart. Some of these tumors, for example myxoma, appear to show principally…
Introduction Undifferentiated sarcomas – tumors for which the cell of origin and/or line of differentiation is unclear – are often subdivided based on their predominant cell shape (e.g., round cell, spindle cell, pleomorphic); while convenient, this is admittedly imprecise since…
Introduction The synovium is one of the more recent phylogenetic developments of the vertebrate locomotor system, with the first synovial joints appearing in the piscine jaw of ancestors of the modern lungfish. Embryologically, the synovium is derived from specialized mesoderm…
The somatic soft tissues do not contain mature osteoblasts or chondrocytes, and these tissues do not typically contain bone or cartilage. However, under certain circumstances, undifferentiated mesenchymal cells are stimulated to differentiate into these specialized cells. This results in a…
Nerve sheath and neuroectodermal tumors are derived from the neuroectoderm or neural crest tissue of the developing embryo. A normal nerve consists centrally of axons, surrounded by Schwann cells ( Fig. 11.1 ). The connective tissue of the axons, including the…
Reactive Vascular Proliferations Papillary Endothelial Hyperplasia Clinical Features Papillary endothelial hyperplasia (PEH) may occur in any location, but most commonly presents in the superficial soft tissues of the extremities, head, and neck. The thumb is a common location. A history…
Clinical Features Symptomatic gastrointestinal stromal tumors (GISTs) affect predominantly middle-aged to older adults, at a median age of 60 years. They are slightly more common in men. Approximately 60% arise in the stomach, and 30% arise in the small intestine; the…
Introduction This chapter will cover two groups of tumors thought to recapitulate features of normal perivascular myoid cells, the myopericytoma family and the glomus tumor family. Although thought at one time to be related, recent molecular genetic evidence suggests different…
Mesenchymal tumors that show skeletal muscle differentiation are rare, and as opposed to other soft tissue tumors, the benign variants (rhabdomyoma) are much rarer than their malignant counterpart (rhabdomyosarcoma). Nevertheless, rhabdomyosarcomas are an important category because they represent the largest…
Smooth muscle neoplasms are categorized by their site of origin; smooth muscle tumors with similar histologic features in different sites vary in terms of their prevalence, clinical behavior, and diagnostic criteria for malignancy. For example, benign smooth muscle tumors (leiomyoma)…