Dedifferentiated liposarcoma (DDL) is a rare, aggressive mesenchymal malignancy of adipose tissue. It often occurs in conjunction with well-differentiated liposarcoma but behaves more aggressively with a greater propensity for developing recurrence or metastatic disease. It can be difficult to diagnose morphologically, especially without a well-differentiated component. DDL most commonly occurs in the retroperitoneum and deep soft tissue, with occurrences in superficial soft tissue being extremely rare. Here we present a case of DDL in an 82-year-old man with an incidental chest wall mass. A core biopsy showed small clusters and single atypical polygonal and spindle cells with large irregular shaped nuclei and prominent nucleoli. Cells were within a vascular stroma containing a prominent mixed inflammatory infiltrate. Immunohistochemistry showed positive staining for SMA and actin. S100, AE1/AE3, ALK-1, CD30 and CD34 were negative. Molecular cytogenetic testing with fluorescence in situ hybridisation showed MDM2 amplification, which confirmed a diagnosis of DDL. Recommended management includes surgical resection, with consideration of radiation or chemotherapy depending on tumour location and risk of recurrence. This unusual case exemplifies the necessity of a thorough work-up that includes a panel of immunohistochemical markers and molecular genetic testing, to aid in the difficult diagnosis of DDL.
Chan et al. (Sun,) studied this question.