DEFINITION

Soft tissue tumors are generally defined as tumors of connective tissues, including nonosseous sarcomas, benign mesenchymal tumors, and tumor-like proliferations. These tumors are usually considered to include non-osseous tumors of the extremities, trunk wall, intraabdominal and intrathoracic space, and head and neck, although definitions vary. Generally excluded from this definition are nonmesenchymal tumors of the skin, cutaneous melanoma, most primary epithelial tumors, and brain and bone tumors.

In this book, soft tissue is understood broadly to include any important tumors of nonbony tissues of the extremities, trunk wall, retroperitoneum, mediastinum, and head and neck, except organ-specific tumors. Gastrointestinal stromal tumors are included because of their clinical importance and common occurrence as metastatic abdominal masses. Cutaneous nevi and primary cutaneous melanoma and intracranial nerve sheath tumors have been excluded. Metastatic epithelial tumors and metastatic melanoma are included because of their practical importance (Table 1.1). As a subspecialty, soft tissue pathology intersects many other subspecialties of pathology.

CLASSIFICATION

The purpose of classification is to group similar tumors to create an understanding of tumor biology and behavior for developing treatment and follow-up strategies. The study of properly classified tumors also aids in the discovery of pathogenesis, devising biology-based treatments, and perhaps preventing tumors.

Soft tissue tumors continue to be classified according to the cell type that they resemble or have been thought to resemble.