as well as other, less commonly altered genes in PLS (e.g. PIK3CA, tyrosine-protein kinase SYK, PTK2B, EPHA5, and ERBB4), may help support but do not clearly define a tumor as being PLS. Extension of the chromosome telomere ends by pathological mechanisms termed alternative lengthening of telomeres occurs in the neoplastic cells of ~80% of PLS cases but is far less common or not seen in the other four forms of liposarcoma. Diagnosis The diagnosis of PLS depends on its presentation, histopathology, and genetics. The histopathology of PLS often closely resembles that of myxofibrosarcoma but is distinguished from that tumor by its content of pleomorphic lipoblasts. Treatment and prognosis Radical surgical resection is the main treatment for PLS; it is also an important palliative intervention to relieve symptoms due to the compression of organs and tissues. Surgery may require removal of an entire compressed organ such as the kidney or colon. Regardless of this surgery, however, local recurrence rates are very high. The uses of chemotherapy and/or radiotherapy in conjunction with radical surgery have not been shown to prolong survival and are regarded as controversial interventions. The National Comprehensive Cancer Network recommends treatment for individuals with high-risk localized PLS by complete surgical resection, when feasible, combined with radiation therapy. Individuals with metastatic disease have been treated with chemotherapy (e.g. doxorubicin plus ifosfamide or eribulin) similar to the regimens used for dedifferentiated liposarcoma (see above section on the treatment of this liposarcoma type) About 20% of PLS tumors metastasize to distant sites, the most common of which are lung (82% of metastases), liver (18% of metastases), and bone or pancreas (18% of metastases). PLS survival rates at 1, 3, and 5 years are reported to be 93%, 75%, and 29%, respectively. Tumors located in the center position of the trunk, larger than 10 cm in size, deeply seated, or containing areas of necrosis have worse prognoses. Myxoid pleomorphic liposarcoma Myxoid pleomorphic liposarcoma (originally termed pleomorphic myxoid liposarcoma) was first described in a large 2009 study of the liposarcomas. While initially regarded as a possible variant of the myxoid liposarcomas with pleomorphic features, the World Health Organization (2020) classified it as a new and distinct form of the liposarcomas. This classification was based on findings that the myxoid pleomorphic liposarcomas, while having histopathological features that were similar to myxoid liposarcomas, had clinical and, most importantly, critical genetic and molecular features that differed from