or a dedifferentiated liposarcoma rather than any other liposarcoma or lipoma form. In addition to the MDM2 and CDK4 genes, this band 13–15 chromosome area also contains the TSPAN31 and HMGA2 genes which, when overexpressed, are associated with various tumors and/or cancers. One or more of these overexpressed genes, it has been suggested, promote and/or contribute to the development and/or progression of ALT/WDL tumors. Diagnosis The diagnosis of ALT/WDL tumors is made based on the features of their clinical presentations, histopathology, and genetic findings. In particular, detection in the ALT/WDL tumor cells of an overexpressed MDM2 or CDK4 gene or the presence of either the specific ALT/WDL-associated sSMC or giant marker chromosome (as defined by next generation DNA sequencing, comparative genomic hybridization, and/or highly specialized cytogenetic G banding analyses) strongly supports the diagnosis of ALT/WDL or dedifferentiated liposarcoma. The clinical presentation and histopathology differences between the latter two liposarcoma forms usually help distinguish between them. Treatment and prognosis ALT/WDL tumors are treated by radical surgical resection to remove all tumor neoplastic tissues. However, these tumors recur locally in 30–50% of cases. Recurrences occur most often in tumors located in less accessible sites such those in the retroperitoneum, mediastinum, and spermatic cord. These less surgically assessible tumors tend to recur repeatedly and ultimately may cause death due to their injurious effects on vital organs. While ALT/WDL tumors have very little potential to metastasize, about 10% will convert to an overtly malignant and potentially metastasizing liposarcoma form, dedifferentiated liposarcoma. The median time for this malignant transformation is about 7–9 years. In addition, a surgically removed ALT/WDL may recur after a variable interval as a dedifferentiated liposarcoma. A large randomized controlled trial comparing radiotherapy followed by surgery to surgery alone in ALT/WDL tumors found little difference between the two regimens. Smaller studies employing selective inhibitors of the protein products of the CDK4 or MDM2 genes implicated in ALT/WDL have shown at best only modest effects. Further studies using these or completely novel treatment regimens are under investigation. A review study in 2012 reported the 5 and 10 year survival rates of individuals with ALT/WDL to be 100% and 87%, respectively. Novel therapies The novel therapies of ALT/WDL are the same as those listed in the Novel therapies section of Dedifferentiated liposarcoma. Dedifferentiated liposarcoma Dedifferentiated liposarcomas are malignant tumors which in ~10% of cases develop in an existing atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDL) tumor