Angiosarcoma Angiosarcomas are malignant tumors that recapitulate many of the functional and morphologic features of normal endothelium. They vary from highly differentiated tumors resembling a hemangioma to anaplastic lesions difficult to distinguish from a poorly differentiated carcinoma or pleomorphic sarcoma. Angiosarcomas are no longer subdivided into lymphangiosarcomas and hemangiosarcomas because this distinction cannot be reliably made by conventional methods. In fact, evidence indicates that some angiosarcomas…

Vascular Tumors of Intermediate Malignancy The term hemangioendothelioma is the designation for vascular tumors that have a biologic behavior intermediate between a hemangioma and a conventional angiosarcoma. Tumors included in this group have the ability to recur locally and some ability to metastasize, but at a reduced level compared to angiosarcoma. The risk of metastases varies within this group from tumor to tumor. For example, epithelioid…

During the 1930s and 1940s, the diagnosis of adult or pleomorphic rhabdomyosarcoma was increasingly made, and most of the rhabdomyosarcomas reported during this period were of this type. These tumors occurred mainly in the muscles of the lower extremity and affected older patients. They displayed a striking degree of cellular pleomorphism, but cells with cross-striations were typically absent. It subsequently became apparent that virtually all of…

Striated Muscle Tissue: Development and Structure Skeletal muscle is formed primarily within myotomes, which are arranged in segmental pairs along the spine and make their first appearance in the cephalic region during the third week of intrauterine life. In the region of the anterior head and neck, skeletal muscle may also develop from mesenchyme derived from the neural crest (mesectoderm). At the earliest stage of muscle…

Leiomyosarcomas account for 5% to 10% of soft tissue sarcomas. They are principally tumors of adults but are far outnumbered even in this age group by more common sarcomas, such as liposarcoma and undifferentiated pleomorphic sarcoma (malignant fibrous histiocytoma). Likewise, they are less common than leiomyosarcomas of uterine or gastrointestinal origin, and only some of the data gleaned from the collective experience with tumors in these…

To a large extent, the distribution of benign smooth muscle tumors parallels the distribution of smooth muscle tissue in the body. The tumors tend to be relatively common in the genitourinary and gastrointestinal tracts, less frequent in the skin, and rare in deep soft tissue. In the experience of Farman, based on 7748 leiomyomas, approximately 95% occurred in the female genital tract, and the remainder were…

Liposarcoma, accounting for 15% to 25% of all sarcomas, is the most common sarcoma of adults. There are several subtypes, which are histologically, biologically, and cytogenetically distinct from one another ( Table 14.1 ). These subtypes range in behavior from nonmetastasizing neoplasms (e.g., atypical lipomatous tumor/well-differentiated liposarcoma [ALT/WDL]) to high-grade sarcomas with full metastatic potential (e.g., pleomorphic liposarcoma). So impressed were Enzinger and Winslow by the…

The significance and multiple functions of fat are not always fully appreciated. Fat serves not only as one of the principal and most readily available sources of energy in the body, but also functions as a barrier for the conservation of heat and as mechanical protection of the underlying tissues against physical injury. Two basic forms of adipose tissue can be distinguished: white fat and brown…

The concept of “malignant fibrous histiocytoma” (MFH) has undergone significant change over six decades, and this term has been supplanted or replaced by undifferentiated pleomorphic sarcoma . The term was introduced in 1963 to refer to a group of soft tissue tumors characterized by a storiform or cartwheel-like growth pattern. They were believed to be derived from histiocytes on the basis of early tissue culture studies…

Fibrohistiocytic tumors of intermediate malignancy originally included only dermatofibrosarcoma protuberans and the closely related giant cell fibroblastoma. This category now embraces other lesions, such as plexiform fibrohistiocytic tumor and soft tissue giant cell tumor. Angiomatoid fibrous histiocytoma, formerly considered a fibrohistiocytic tumor of intermediate malignancy, is better considered a translocation-associated mesenchymal tumor of uncertain type (see Chapter 32 ). All the fibrohistiocytic tumors of intermediate malignancy…

The concept of fibrohistiocytic neoplasms has been challenged largely because the malignant forms (i.e., malignant fibrous histiocytoma) consistently lack histiocytic features, and because some, when carefully studied, show a subtle degree of differentiation. Nonetheless, many benign fibrohistiocytic lesions are truly derived from histiocytes (e.g., solitary xanthogranuloma, xanthoma), so there remains some merit in retaining this category. This has been endorsed by the World Health Organization (WHO),…

Although previously grouped together in this textbook, superficial and deep fibromatoses are now discussed separately because of distinct differences in clinical behavior. The superficial fibromatoses are described with the benign fibroblastic/myofibroblastic proliferations (see Chapter 7 ). Deep fibromatoses are included in this chapter, which focuses on fibroblastic/myofibroblastic tumors of borderline and malignant behavior. This chapter also describes congenital/infantile fibrosarcoma and inflammatory myofibroblastic tumor (previously discussed with…

Fibrous tumors of infancy and childhood can be divided into two large groups: (1) lesions that correspond to similar lesions in adults in terms of clinical setting, microscopic picture, and behavior (e.g., nodular fasciitis, palmar/plantar fibromatosis, abdominal/extraabdominal fibromatosis) and (2) fibrous lesions that are peculiar to infancy and childhood and generally have no clinical or morphologic counterpart in adult life. The lesions in the second group…

Fibrous connective tissue consists principally of fibroblasts and an extracellular matrix (ECM) containing fibrillary structures (collagen, elastin) and nonfibrillary ECM, or ground substance. Dense fibrous connective tissue, such as that found in tendons, aponeuroses, and ligaments, is composed predominantly of fibrillar collagen, whereas loose fibrous connective tissue contains a relative abundance of nonfibrillary ground substance. Fibroblasts are the predominant cells in fibrous connective tissue. These cells…

Immunohistochemistry (IHC) is the use of antibody-based reagents for localization of specific epitopes in tissue sections. Over the past several decades, IHC has become a powerful tool to assist the surgical pathologist in many clinically critical settings. It is important to recognize that IHC has two components, each with its own strengths and weaknesses. These components may be thought of as the “hardware” (i.e., antibodies, detection…

Clinical Information The diagnosis of a soft tissue lesion requires a modicum of clinical information and adequate, well-processed tissue. At a minimum, the pathologist should be apprised of patient age, tumor location, and its growth characteristics. In some cases, the results of imaging studies, particularly magnetic resonance imaging (MRI), enhance one’s understanding of the clinical extent of the lesion and its relationship to normal structures (see…