Search

As proof that cancers can occur in essentially any cell type, antigen-presenting cells (e.g., dendritic cells or Langerhans cells) can form cancers. Since these tumors can arise from lymph nodes, but do not arise from lymphocytes themselves, they are sometimes termed sarcomas. Other pathologists use the more noncommittal term “tumor” instead of “sarcoma” in this context. If anything, sustentacular tumors of lymphatic tissue represent the correct use of the term “histiocytic sarcoma,” as opposed to malignant fibrous histiocytoma (MFH, now termed undifferentiated pleomorphic sarcoma [UPS]), which are not composed of histiocytes, as are these tumors.

Osteogenic sarcoma can arise in soft tissue, although it is much more commonly observed as a primary bone tumor. There is debate as to whether extraskeletal osteogenic sarcoma (ESOS) should be managed as a soft tissue or a bone tumor. Biologically, the tumor is typically the osteoblastic subtype and can arise spontaneously or after irradiation.

Fibrosarcoma can occur at all ages (Fig. 12.1) and in all sites (Fig. 12.2). Before the era of immunohistochemistry, fibrosarcoma was one of the most common diagnoses for a soft tissue sarcoma. With the development of immunohistochemical and molecular techniques, it is now rare for a sarcoma to be termed a fibrosarcoma, which by its name implies fibroblasts as the cell of origin. With increasing sophistication in diagnosis, more and more subtypes of fibroblastic sarcomas are now appreciated, all relatively rare tumors.

The most common term for a generic high-grade sarcoma has evolved over the years from fibrosarcoma to malignant fibrous histiocytoma (MFH) and now to high-grade undifferentiated pleomorphic sarcoma (UPS). The new nomenclature is utilized to differentiate this tumor from tumors that are truly histiocytic, i.e., histiocytic sarcoma, recognizing that the microscopic morphology of such tumors was not specific for sarcomas. Specific varieties of what was called MFH in the past have proved to be unique entities. For example, myxofibrosarcoma is now a clearly defined sarcoma subtype that was formerly termed myxoid MFH. Myxofibrosarcoma occurs more frequently in the subcutaneous tissue and has infiltrating pattern (Fig. 7.1). Angiomatoid MFH is reclassified as angiomatoid fibrous histiocytoma, having mostly a benign clinical course and occurring in children and young adults. The situation is further complicated since the term MFH is still employed in the bone (and treated most commonly as osteogenic sarcoma in children).

One of the few known causes of sarcomas is therapeutic irradiation. Therapeutic radiation has also been associated with development of breast cancer, lung cancer, and accelerated coronary artery disease in patients receiving thoracic radiation [1, 2]. With the increased recognition of second cancers as a long-term side effect of radiation therapy, some attempts have been made to use radiation more sparingly; however, for reasons unclear to the authors, use of therapeutic radiation is even more widespread than in the past, with the use of tylectomy and radiation therapy, a recognized standard of care for ductal carcinoma in situ of the breast, despite the ability to obtain negative margins in at least 95 % of patients with surgery alone [3, 4]. The incidence of a sarcoma after radiation is not precisely known and may vary from one part of the body to the next. In a series of patients treated for cancer of all sites in Finland, for example, the crude risk was of the order of 0.05 % [5].

Is it a sarcoma or is it a melanoma? Clear cell sarcoma (CCS), also called clear cell sarcoma of tendons and aponeuroses [1, 2], has features of both. CCS represents perhaps 1 % of all sarcomas. Since it starts in soft tissue and usually does not affect skin [3], CCS is anatomically distinct from melanoma. Patients are typically younger, between 15 and 45 years of age, and women are more commonly affected than men. The foot and ankle are common primary locations for this rare sarcoma. Age and site distribution for adult patients are shown in Figs. 18.1 and 18.2.

Gastrointestinal stromal tumors (GISTs) have been recognized as a distinct biological entity since 1998. Previously GISTs were considered to be smooth muscle neoplasms often classified as leiomyosarcoma or gastrointestinal autonomic nerve tumors (GANT) or combinations of both. Definition and cellular origin are suggested to be the interstitial cell of Cajal [1]. They commonly present as mass lesions, intra-abdominally, often of large size and with rupture and/or metastatic disease. Gastrointestinal stromal tumors make up one-third of all visceral sarcomas (Fig. 4.1). Our original report [2] described 200 gastrointestinal stromal tumors, which was approximately 6 % of the 3,500 patients with sarcoma admitted to our institution. Age and sex distribution are shown in Fig. 4.2, and lesions are distributed in the stomach, more than in the small intestine and more than in other sites (Fig. 4.3). An example of a GIST of the stomach is demonstrated in Fig. 4.4.

Beyond leiomyosarcoma, uterine sarcomas and tumors that contain “sarcoma” in the name (i.e., carcinosarcoma) are well-recognized biological entities. The three nonleiomyosarcoma tumors, (low-grade) endometrial stromal sarcoma, high-grade undifferentiated stromal sarcoma, and mixed Mullerian tumors including carcinosarcoma, are all very different from one another biologically. They are often omitted in discussions of soft tissue pathology as different groups of pathologists generally review such cases in expert centers than those who review soft tissue or bone tumors. Age distribution for adult uterine endometrial stromal tumors is shown in Fig. 21.1.

Several types of sarcomas are more common in children, the most common of which include osteogenic sarcoma, Ewing sarcoma, and rhabdomyosarcoma. While osteogenic sarcoma presents similarly in children and adults under age 40, there are a variety of differences in the presentation of Ewing sarcoma in adults versus pediatric patients. Ewing sarcoma is predominantly a bone tumor in children, while in adults it occurs much more commonly in soft tissue. As is also noted below, there is a new class of sarcomas that are similar in appearance to Ewing sarcoma but contain translocation products other than the classical t(11;22) EWSR1-FLI1 translocation. Pleomorphic rhabdomyosarcoma is much more common in adults than in children, while alveolar rhabdomyosarcoma is rare in adults.

Desmoplastic small round cell tumor (DSRCT) is a somewhat chemotherapy-sensitive, but highly lethal, sarcoma diagnosis. Distribution by age for adults is shown in Fig. 19.1, emphasizing that it is an uncommon tumor, seen mainly in adolescents and young adults (age 15–30). There is a strong male predominance (∼5:1) and nearly always affects the peritoneum as multifocal/metastatic disease (Fig. 19.2). The best outcomes from therapy are those who have both a good response to chemotherapy (using agents typically employed for Ewing sarcoma) and successful surgical debulking [1]. Rare patients will present with disease elsewhere; if disease is localized, the cure rate is expected to be higher than the 5–15 % typically encountered for those patients with primary abdominal disease [1, 2].