Non-retroperitoneal dedifferentiated liposarcoma (DDLS) is relatively uncommon and its characterization at the molecular genetic level has been limited. We describe the cyto­genetic and molecular cytogenetic findings of giant DDLS arising in the right thigh of an 83-year-old woman. Magnetic resonance imaging revealed a mass composed of two components with heterogeneous signal intensities, suggesting the coexistence of a fatty area and another soft tissue component. A wide resection of the tumor was performed. The resected, grossly hetero­geneous mass, measuring 26x18x8 cm, was histopathologically composed of a well-differentiated liposarcomatous component transitioning abruptly into a dedifferentiated one. Cytogenetic analysis exhibited a complex karyotype with several numerical and structural alterations, including ring and giant marker chromosomes. Metaphase-based comparative genomic hybridi­zation analysis showed high-level amplifications of 1q21-q25 and 12q13-q21. Interphase fluorescence in situ hybridization analysis revealed MDM2 and CDK4 gene amplification in both the well-differentiated and dedifferentiated components. These findings indicate that DDLS of the extremity shares a similar genetic background to retroperitoneal DDLS.

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