Soft tissue sarcomas are a complex family of rare malignant neoplasms that show mesenchymal differentiation. Benign soft tissue tumors are more common than their malignant counterparts. Both benign and malignant mesenchymal tumors can cause diagnostic confusion. The previous chapters of…
Since the initial description of pseudosarcomatous fibroepithelial stromal polyps of the distal female genital tract in the early 1960s, various relatively site-specific mesenchymal lesions of the lower genital tract have been recognized. These lesions are often diagnostically challenging because of…
Epithelial neoplasms predominate in the gastrointestinal (GI) tract, as they do in all parenchymal organs and organ systems. However, a wide array of mesenchymal neoplasms also arises in the GI tract, some of which are exclusive or nearly exclusive to…
Cutaneous mesenchymal tumors are considered separately in this chapter because many of the tumors are either unique to or predominate in the skin or show specific features when presenting in the skin. The morphologic spectrum of cutaneous soft tissue tumors…
Soft tissue tumors and other mass-forming lesions exhibiting osteocartilaginous differentiation are commonly encountered in diagnostic soft tissue pathology. They comprise diverse entities with distinct clinicopathologic features and clinical behaviors. However, it is important to remember that, occasionally, nonmesenchymal tumors may…
The vascular system is composed of arteries and veins and their derivatives, capillaries, and lymphatic channels. Although large arteries and veins are readily distinguished histologically, their smaller counterparts can be difficult to differentiate morphologically. In general, veins have a thinner…
Adipocytic tumors represent an extremely heterogeneous category of clinically and morphologically distinctive lesions, sharing variable amounts of lipomatous differentiation. Some of them (i.e., benign lipomas and well-differentiated liposarcoma [WDLPS]) are among the most commonly encountered mesenchymal neoplasms. As will be…
Multinucleated giant cells are seen in small numbers in a diverse range of soft tissue tumors. Similarly, soft tissue tumors with prominent giant cells compose a heterogeneous group of benign, intermediate, and malignant neoplasms. Recognition of the various types of…
Although a sparse lymphocytic infiltrate is relatively common in mesenchymal neoplasms, few histologic types of soft tissue tumors characteristically contain prominent inflammatory cells. In some such cases, the presence of an inflammatory infiltrate can be a diagnostic clue, whereas in…
Soft tissue tumors with biphasic histology are uncommon. The “biphasic” designation is often applied to tumors with mixed spindle cell and overtly epithelial (often glandular) components but can also be applied to tumors with mixed spindle cell and epithelioid morphology…