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…
The term small round blue cell tumors is used to refer to a group of generally highly aggressive malignant neoplasms, seen under the microscope as monotonous proliferations of small cells with scant cytoplasm. This category classically includes certain subtypes of…
Pleomorphic sarcomas are defined as malignant mesenchymal neoplasms characterized at a histologic level by prominent cellular pleomorphism and often brisk mitotic activity, with or without a readily identifiable line of differentiation. Cellular pleomorphism in mesenchymal neoplasms is probably best defined…
The group of epithelioid mesenchymal tumors encompasses neoplasms that are composed, partly or extensively, of rounded or polygonal cells, at least somewhat resembling epithelial cells ( Boxes 6.1 to 6.3 ). These tumors show variable, sometimes misleading growth patterns, including…